''Top of the basilar'' syndrome
Louis R. Caplan
Neurology 1980;30;72
DOI 10.1212/WNL.30.1.72
This information is current as of January 1, 1980

The online version of this article, along with updated information and services, is
located on the World Wide Web at:
http://www.neurology.org/content/30/1/72.full.html

Neurology ® is the official journal of the American Academy of Neurology. Published
continuously since 1951, it is now a weekly with 48 issues per year. Copyright © 1980 by the
American Academy of Neurology. All rights reserved. Print ISSN: 0028-3878. Online ISSN:
1526-632X.

opinions 8. reviews
Article abstract-Infarction of rostral brainstem and cerebral hemispheral regions fed by the distal basilar artery
causes a clinically recognizable syndrome characterized by visual, oculomotor, and behavioral abnormalities, often
without significant motor dysfunction. Rostral brainstem infarction produces oculomotor and pupillary signs that
are identical to those in thalamic hemorrhage. Somnolence, vivid hallucinations and dreamlike behavior may also
accompany rostral brainstem infarction. Temporal and occipital infarctions are frequently accompanied by
hemianopia with distinctive characteristics, fragments of the Balint syndrome, amnestic dysfunction, and agitated
behavior. The “top of the basilar” syndrome is most often due to an embolus.
NEUROLOGY 30: 72-79, January 1980

'"rap of the basilar” syndrome
Louis R. Caplan, M.D.
Occlusive vascular disease of the rostral basilar
artery frequently causes infarction of midbrain,
thalamus, and portions of the temporal and occipital lobes fed by posterior communicating and posterior cerebral arterial tributaries of the basilar
artery. Clinical signs include a n array of visual,
oculomotor, and behavioral abnormalities, usually without prominent motor dysfunction, which
may confuse those inexperienced with these findings. Segarra’ used the term “the syndrome of the
mesencephalic artery” to describe rostral paramedian brainstem infarction, and analyzed one type
of b e h a v i o r a l m a n i f e s t a t i o n (“somnolent
mutism”). Others have described clinicopathologic
aspects of isolated neuroophthalmologic2~1sand
b e h a v i ~ r a l l ”features.
~~
This report, based principally on experience from personally examined
cases with autopsy, computerized tomography
(CT), or angiographic verification, reviews the
major clinical features. Aspects of the syndrome
considered i n detail elsewhere (e.g., memory
10ss20,22333-M
and alexia without agraphia? are
given only passing attention. The “top of the basilar” syndrome is a recognizable subdivision that
can be distinguished from the large group of heterogeneous conditions usually lumped together
under the term “vertebrobasilar ischemia” or “insufficiency.”
Infarction of rostral brainstem and posterior
hemispheres often coexists because of the common
vascular supply. However, because either may
occur in isolation, i t is appropriate to consider
brainstem and hemisphere manifestations separately.

Part I. Rostral brainstem infarction. Visual de-

fects Disorders of ocular movement. Oculomotor
dysfunction in patients with bilateral ischemia of

rostral midbrain and posterior thalamus is indistinguishable from that in patients with thalamic
h e m 0 r r h a g e . ~ 5The
* ~ ~signs include:
Disorders of vertical gaze. Voluntary or reflex
vertical gaze (tested by oculocephalic and caloric
maneuvers a n d Bell phenomenon) is 6ften
abolished. One or both eyes may rest in a downward position. Isolated paralysis of upward or
downward gaze occurs less frequently. In human
patients with vertical gaze paralysis due to vascular disease, bilateral lesions are found in the midbrain t e g m e n t ~ m . ~ . 1Iln* monkeys
~~
and h u mans,4’11lesions of the pretectum, in the region of
the posterior commissure, are necessary to produce paralysis of upward gaze. Isolated downward
gaze palsy is rare, and may be associated with
lesions medial and dorsal to the red nucleus;**e
lesions causing paralysis of downward gaze are
more ventral and caudal in the midbrain tegmentum than those responsible for deficits of upward
gaze.
Disorders of convergence. One or both eyes may
rest in an inward position. Hyperconvergence or
convergence spasm may be observed when the patient attempts conjugate lateral or vertical gaze.
Convergence retraction n y s t a g m ~ sa, ~rhythmic
~
inward beating movement of the eyes, may be
spontaneous, but is best elicited by having the
patient fix on a n optokinetic stimulus which is
moving upward.
“Pseudosixth.” This sign, described by Fisher,%
refers to failure of ocular abduction which is not
due to dysfunction of the sixth nerve. The sign is
frequently bilateral and is accompanied by
“hyperconvergence.” Failure of the eye to abduct is
due to two mechanisms: (1) Fixation with the
hyperconvergent eye (the right eye in figure 1).
When t h e hyperconvergent eye i s covered,
~

~~

From the Department of Neurology, Beth Israel Hospital, and Harvard Medical School, Boston, MA.
Accepted for publication June 11, 1979.
Address reprint requests to Dr.Caplan, Chairman, Department of Neurology, Michael Reese Hospital, 29th and Ellis Streets. Chicago, IL 60616.

72 NEUROLOGY 30 January 1980

Figure 1 . “Pseudosizth” phenomenon. (A) Forward
gaze. Right eye i s down and in; left eye is neutral.
(B) Conjugate gaze to the left. Right eye converges
strongly. Left eye fails to abduct fully and adducting
jerks are visible.

midbrain infarction which help to distinguish the
two entities. Computerized tomography (CT)documenting the absence of a supratentorial spacetaking lesion is often a necessary corroborative
diagnostic procedure. A unilateral lesion of the
third nerve nucleus may cause severe bilateral
~tosis.~*‘
Pupils. Diencephalic dysfunction may interrupt
the afferent limb of the pupillary light reflex arc.13
Bilateral sympathetic dysfunction usually accompanies the lesion, so that the pupils are small and
the reaction to light is often transient and of small
magnitude. A magnifying glass may be needed t o
separate the tiny, poorly reactive pupils of
thalamic disease from small, reactive “pontine
pupils.” With lesions more caudal in the midbrain,
large or midposition fixed pupils are caused by
dysfunction of the Edinger-Westphalnucleus or its
fibers.
The pupil can quickly assume an eccentric position in the iris, a phenomenon called “corectopia
iridis.” The pupil may shift from a central position
to an eccentric one intermittently, a sign characteristic of midbrain lesions12*14
Three examples of rostral brainstem infarction
illustrate the neuroophthalmologic findings.

monocular fixation by the abducting eye on a distant object far to the side may elicit further abducting movements. (2) Convergence vectors are also
present in the abducting eye and neutralize or
counteract conjugate lateral movements. If the
abducting eye is watched carefully, convergence or
adducting jerks of the abducting eye are often
Case 1. An elderly diabetic woman suddenly became
present.
sleepy and unresponsive. Her left eye was deviated latElevation and retraction of the upper eyelids
erally and the left pupil was midposition and fixed. The
(Collier sign)5 may be unilateral or bilateral; GS
right eye was deviated down and in, and had frequent
traction of one eyelid may contrast with a droop of
convergent inward movements. Neither eye moved verthe opposite lid.
tically (either voluntarily or reflexly). On attempted
Sudden darting or lightning-like oscillations of
conjugate lateral gaze, each eye could abduct but did not
the eyes may complicate horizontal or vertical
reach the lateral canthus. The right pupil was 2 mm and
gaze.”
had a transient and minimal reaction to light. Right
Skew deviation (ocular divergence in the vertihemiplegia, hypesthesia to pinprick on the right half of
cal plane) has been documented in lesions of the
the body, and bilateral Babinski signs were present.
examination revealed a fresh organizing
middle cerebellar peduncle and r n e d ~ l l a . ~ ~ . ~ Postmortem
Q
myocardial infarction. There was a n old cystic infarction
“Midbrain skew” has been inferred by Smith,
in the right caudate nucleus, putamen, and internal
David, and K l i n t w ~ r t because
h ~ ~ of accompanying
capsule. A fresh necrotic lesion (figure 2) due to embolic
signs of dysfunction of the pupils and third nerve
infarction
involved the distribution of the left superior
believed clinically localized to the periaqueductal
cerebellar and left posterior cerebral arteries. The regray region of the midbrain. Autopsy verification
gion of the left third-nerve nucleus in the midbrain,
of a rostral brainstem cause of skew deviation is
periaqueductal gray region, red nucleus and cerebral
uncommon, but is provided by cases 1 to 3 (depeduncle were infarcted. The left superior cerebellar
scribed below).
surface was also infarcted. There was a tiny infarction in
Vertical nystagmus,* conjugate horizontal nysthe left ventrolateral thalamus.
tagmus, and ocular bobbing are not associated
with high brainstem infarction.
Case 2. An 81-year-old woman suddenly believed the
When infarction is more caudal and includes the
lights had been shut off while she was reading. There
was complete bilateral ptosis; she could not open either
midbrain tegmentum ventral to the aqueduct,
eye. Pupils were 2 mm, and pupillary light reaction was
internuclear ophthalmoplegia or third-nerve palslight, delayed, and transient. The eyes were deviated
sies are present. Bilateral infarction of the third
conjugately to the right with slight downward positionnerve nucleus and adjacent reticular formation
ing of the left eye. Right conjugate gaze was full; on left
causes hypersomnolence and third nerve palgaze, there was slight adduction of the right eye and only
sies,24.= difficult to distinguish clinically from the
minimal abduction of the left eye. There was no vertical
brainstem dysfunction of transtentorial herniagaze. She was hypersomnolent for 1week and exhibited
tion. The sudden onset and the absence of severe
transient right visual inattention.
headache, vomiting, or hemiplegia prior to the apPostmortem examination in another hospital years
after the stroke’ revealed a cavitary lesion of the midpearance of stupor are characteristics of primary

January 19%0 NEUROLOGY 30 73

brain involving the right third nerve nucleus, right medial longitudinal fasciculus and right fourth nerve region and some of the medial right red nucleus dorsally.
The lesion extended to the midline dorsal structures, but
spared the left third nerve region and the ventral regions of the brainstem.
Case 3. After 4 days of dizziness and unsteady gait, an
80-year-old woman suddenly collapsed. The right pupil
was 2 mm and fixed. The eyes did not move past the
midline to the right on oculocephalic or caloric stimuli,
but these maneuvers elicited full left gaze. Vertical gaze
could be elicited by oculocephalic reflexes. There was a
right hemiplegia, right hemisensory loss and right
hemianopia. She remained mute. Subsequently, the
right eye moved to a down and in position and, on right
gaze, the right eye did not abduct as well as the left
adducted, but conjugate gaze to the right was possible.
Postmortem examination revealed occlusion of the
rostral basilar artery with thalamic and midbrain infarction and bilateral posterior cerebral artery territory
infarction, more extensive on the left.

Behavioral abnormalities. Somnolence. Sleepiness, apathy, and lack of attention t o the environment result from infarction of the rostral medial
reticular formation due t o occlusion of the
mesencephalic artery (the proximal portion of the

74

NEUROLOGY 30 January 1980

posterior cerebral artery) or its penetrating
branches. Facon, Steriade, and WertheinZ4described a patient with bilateral third nerve palsies
who remained in a sleeplike state for 3 years.
Postmortem examination revealed occlusion of the
top of the basilar artery and a paramedian infarction in the midbrain and anterior thalamus. Castaigne and associatesz5described a patient with a
butterfly-shaped infarction destroying intralaminar nuclei, the medial part of the centrum
medianum, third nerve nuclei and part of the
brachium conjunctivum; hypersomnolence and
ophthalmoplegia were the major findings.
Segarral used the term “somnolent mutism” to
characterize the behavior of patients with high
medial brainstem infarction and contrasted it with
the “coma vigil” of patients with bilateral cerebral
lesions.
Peduncular hallucinosis. Hallucinations occur
but are rare in patients with high brainstem infarction. They may occur without visual field defects. These hallucinations are usually vivid and
well-formed. One patient with a clinically unilateral midbrain and thalamic infarction saw a colored parrot with beautiful plumage off to his right,
and another patient with episodic posterior
hemispheral ischemia awakened at night and saw

pictures of his grandmother flashed on the wall to
his left, as if projected in a home movie. Rarely, the
same patient heard a knocking noise, as if rocks
were in a car engine. Though vivid to the patients,
the hallucinations were always recognized as
somehow not “real.”
The term “peduncular hallucinosis” was used in
a review by van Bogaert32to describe strange hallucinations, usually visual, in patients with midbrain lesions. (The term “pdonculaire,” when used
in this context, refers to the midbrain, not necessarily the cerebral peduncle.) Anatomic verification of this phenomenon is scanty. Lhermitte,27
who was the first to introduce this term, described
a patient in detail. A 72-year-old woman complained of vertigo and subsequently developed
headache, vomiting, and bilateral sixth nerve palsies. Left ophthalmoplegia, a left central scotoma,
and intention tremor of both arms subsequently
developed. She had vivid hallucinations of
animals-cats and chickens, with strange appearances. She also saw children at play with toys. A
child would suddenly change into an old woman.
She would try to touch the images, but was aware
that they were not real. She also had insomnia a t
night and slept a great deal during the day. Hallucinations occurred only during late daylight
hours, especially at sundown. There was no
anatomic verification, but the lesion was thought
to be a vascular brainstem lesion. Alajouanine,
Thurel, and DurUptz1described another patient,
studied only clinically-a young man with a sudden hemiplegia and hemianesthesia following
amputation of an infected limb. Nystagmus and
ophthalmoplegia indicated a brainstem lesion. He
saw blood and red hair descending toward the bed,
and had vivid imaginings of being vertically
placed on an ambulance bed amid animals. This
was a febrile, ill patient, again without anatomic
verification.
A single pathologically verified case of peduncular hallucinosis concerned a patient with a clinical
lesion of the red nucleus31 who died 14 months
later.32 A 59-year-old woman with rheumatic
heart disease developed vertigo, double vision, and
ataxia. The major findings were a right third nerve
palsy, dysmetria of the left limbs, left hyperreflexia, and gait ataxia. From the onset, she had
vivid hallucinations accompanied by severe agitation. The hallucinations always occurred in the
evening; she remained calm and unaffected during
the day and the remainder of the night. On the
wall opposite her, she would see the head of a dog
or an image of a horse or a green serpent against a
red background. The images appeared and disappeared and were never fixed. Intricate lines, odd
colors, and images persisted for 1 to 2 hours, and
then ceased. A t postmortem examination 14
months later,32 an infarct was seen in the left
midbrain, primarily affecting the superior cerebel-

lar peduncle, cerebral peduncle, substantia nigra,
red nucleus, and periaqueductal gray region.
Baruk40 and Reeves and Plum41 commented that
other lesions along the base of the brain, affecting
the diencephalon and midbrain, could precipitate
hallucinations.
The pathologic anatomy and physiology of these
hallucinations is not clear; they may be related to
an abnormality of nonspecific cortical excitation
(reticular formation), or abnormal stimulation or
deafferentation of specialized thalamic nuclei
(e.g., lateral geniculate). Similar visual hallucinations in the evening (“sundowning”) are common
in elderly patients without cerebrovascular disease.
Fischer-Perroudon, Mouret, and J o u ~ e ret~~
ported a patient with distal limb pain and diarrhea
in whom polygraphic EEG recordings confirmed
total insomnia. Dramatic hallucinations occurred
only between 9 and 11P.M. The hallucinations disappeared after administration of 5-hydroxytryptophan had caused a return to normal sleep.
No central nervous system lesions were found
on postmortem examination.
An abnormality of sleep may be the essential
factor, and was present in our patients with
hallucinations and in those previously reported.
More detailed clinicopathologic correlation is
needed to verify the origin and nature of this
phenomenon. The pathologic anatomy responsible
for this type of hallucination is probably not
limited to the midbrain alone.
“Unusual reports.” Patients with rostra1
brZnsteminfarEtiCn may reply in a bizarre way to
queries requiring orientation. For example, one
bedridden patient, when asked her whereabouts,
replied that she was on the beach at Nice sunning
herself in a bikini. Another patient excused herself
from replying to a question because she was speaking to some friends on the telephone, and proceeded to hold an imaginary phone before her as if
to speak. These reports are similar to those given
by patients with metabolic encephalopathy or
frontal lobe disease.
The unusual reports have had the following
characteristics: (1)They are influenced by stimuli,
e.g., pictures or preceding conversation in a patient’s room. A patient in whose room a native
picture by Gauguin hung on the wall reported that
she was in Tahiti. Another patient, when conversation nearby concerned travel, reported she was
on an airplane. (2)They have no approximation to
reality. Patients with amnestic disorders such as
the Wernicke-Korsakoff syndrome are frequently
not oriented exactly to place, but they generally
give an approximate answer after looking about
for clues. For example, in a hospital they will supply the name of a medical facility with which they
are familiar. The patient with high brainstem disease frequently replies without exploring the en-

January 1960 NEUROLOGY 30 75

vironment, and answers are bizarre. (3)Observations or questions of the interviewer are incorporated into the reply. For example, a patient reported that he was driving a car headed toward
Beacon Street. When asked who the questioner
was, he replied, “You are a policeman, and you
must get out of the way of the car or you will be
hit.” Patients with unusual reports have all had
disturbances of wakefulness, characterized by
periods of sleep or drowsiness. Stuss and ass o c i a t e ~consider
~~
this an extraordinary form of
confabulation; their patients all had frontal lobe
disease and the confabulation was attributed to
altered frontal lobe function.
Some patients with this phenomenon of “unusual reports” have commented that they “dream
a lot” and often “cannot tell dreams from reality.”
Patients recovering from general anesthesia and
normal individuals awakening from sleep frequently have difficulty determining if a mental
concept arose from an actual event or from a
dream. Even in the fully awake, normal individual, thoughts somewhat extraneous to the
practical matters at hand are frequent distractions. The prose of James Joyce and Virginia Woolf
contains easily recognizable examples of the
stream of consciousness that is familiar to all of us.
The unusual reports and dreams are equally
characterized by suggestibility from environmental factors and frequent absurdity. The anatomic
substratum that helps us separate dreams or
thoughts from reality is unknown. The appearance
of dream confusion in sleeplike twilight states and
anesthesia suggests a disturbance of nonspecific
alerting systems, e.g., the reticular activating system and thalamic nuclei stimulating hemispheral
regions. This could explain the presence of these
reports in disease of either brainstem or cerebral
hemispheres. Unusual reports, somnolence, and
hallucinations may all be related signs of dysfunction of the rostra1 reticular formation of the
brainstem.

Part 11. Posterior cerebral artery territory
hemisphere infarction. A. Unilateral infarction. Visual defects. Hemianopia. A homonymous
field defect may result from a lesion anywhere in
the visual radiation, from optic tract to calcarine
cortex. Several features identified in 15 cases of
CT-confirmed unilateral occipital infarction were
correlated with lesions in or near the calcarine
cortex within the posterior cerebral distribution,
as opposed to more anteriorly placed lesions in
the territory of the middle cerebral artery.
Awareness of the visual deficit. Patients with
posterior cerebral artery lesions often complain of
a void or blackness to one side. In middle cerebral
artery parietal lesions, the field deficit is usually
accompanied by visual neglect, and the visual defect is usually not noticed or acknowledged by the

76

NEUROLOGY 30 January 1980

patient.
Preservation of optokinetic nystagmus. Cogan’s
rule that optokinetic nystagmus is lost in an occipital lobe mass lesion but preserved if the occipital
lobe lesion is vascularu holds up well. Temporal or
parietal lesions in middle cerebral artery territory
are usually associated with loss of optokinetic nystagmus to the side of the hemianopia.
Partial vision within a hemianopic field. Patients with a calcarine infarction may, on occasion,
identify the color, nature or size of an object within
the “blind field”; in lesions of the middle cerebral
artery territory that interrupt the visual radiation, vision is usually all-or-nothing.
Homonymous but differing involvement of
superior and inferior quadrants in a hemianopic
field. This imdies uneaual involvement of both
banks of the chcarine fiisure and is less common
in patients with lesions of the optic radiations.
Scintillations at the edge of a hemianopic field.
Patients with occipital lesions frequently note
poorly formed scintillations in the hemianopic
field as a presenting symptom of posterior cerebral
artery occlusion.2 Scintillations also occur when
the defect is clearing and usually involve the partially affected edge of the hemianopic field. They
are so commonly seen (5/15 patients) that I usually
warn the patient not to be concerned if they appear.
Visual perseverations. Perseverations may take
one of several forms. (1)Seeing a n object repeated
toward the hemianopic side; a train of individuals
may seem to be repeating within the affected field.
(2) If the patient looks toward the hemianopic
field, he may continue to see an image that had
previously been in front of him. (3) Persistence of
an image in the center of the field of vision after
the image has moved. The first two types of visual
perseveration have been seen in patients with
posterior cerebral artery disease and are not a part
of dysfunction due to lesions within the middle
cerebral zrtery territory.
Absence of visual neglect. Patients with occipital
infarction do not usually neglect the hemianopic
field. They read a full paragraph or headline, copy
a full diagram if given time, and do not neglect one
side of space when asked to bisect lines. At the
onset of the deficit, however, especially if objects
are shown tachistoscopically and quickly, there
may be a transient tendency to neglect part of the
visual field.
Behavioral defects. Left occipital infarction may
be accompanied by anomic aphasia,22alexia without agraphia,22 a temporary Korsakoff-like amnestic syndrome, 1oao*22 or visual a g n o ~ i a . ~ ~ ~ ~ ~ . ~
Right occipital infarction has been associated with
the Charcot-Wilbrand syndrome of defective revisualization and absence of visual dreaming and
a p r o s ~ p a g n o s i athough
,~~
the latter is generally
associated with bilateral infarction. These syn-

I

dromes have been reviewed el~ewhere.1~

B. Bilateral infarction. Visual defects. Cortical
blindness. Cortical blindness is the most severe
visual defect caused by bilateral occipital infarction. Symonds and Mackenziel8 reviewed clinical
and pathologic aspects of this syndrome and identified embolus as the most common vascular etiolon.
The Balint syndrome. Elements of the Balint
~ p X m e l 5are
. ~ frequently
~
found in infarcts of
the territory of both posterior cerebral arteries.
The major characteristics are:
Asimdtagnosia, or difficulty viewing the whole
visual field at once. Patients mav see things
piecemeal and identify a part insteadof the whok.
Useful techniques to elicit this phenomenon include asking the patient to: (1) enumerate the
number of objects on a paper (letters, words, crosses, or circles), (2) identify a number of objects
shown simultaneously, (3) explain the action in a
cartoon or picture, and (4) read a paragraph. Patients with the Balint syndrome usually cannot
read a paragraph because they omit words or
whole lines. They can, however, read individual
words and letters, in contrast to patients with
alexia without agraphia. They may have considerable difficulty describing the action in a picture or
cartoon, or comparing parts of a picture.
Optical apraxia, or poor hand-eye coordination.
Patients may do better with hand motions when
not under visual control, e.g., touching the hand to
the nose with eyes closed. “racing a line diagram
or pointing to a precise part of an object in a picture
are useful in studying this problem.
A rmia o aze. These patients cannot look
w ere t ey esire. Ask the patient to look at one
object and then direct gaze to another. Watch the
patient observe a picture or scene.
Balint syndrome may occur without major field
defects on tangent screen or perimetry. The normal person perceives a central percept and then
searches the visual environment to amplify information concerning that initial cue. This leads to
further perception and further searching.33 Looking and seeing are related functions, but with different anatomies. In the patient with the Balint
syndrome, the anatomic connections between occipital and parietal lobes are disrupted, impeding
fine interactions between perception and looking.
Metamorphosia. Alteration in size, shape, or
angulation of objects is an infrequent feature of
cerebrovascular lesions. When i t occurs, it is
nearly always associated with bilateral occipital
or occipitotemporal lesions. Patients may complain of enlargement (macropsia) or diminution
(micropsia) of objects. The size alteration may be
limited to one half-field or quadrant, giving objects
a grotesque appearance. Patients may be unable to
recognize distance relationships of objects within

*

the environment and may have diffkulty comparing distant objects with respect to size and depth.
Other patients have complained of sharp angulation of objects, with the room appearing turned or
upside down. When not related to an ocular muscle
disorder causing vertical diplopia, this always
means a posterior hemispheral lesion.
Behavioral abnormalities. Memory. Defects in
the acquisition of new information and memory
occur in patients with bilateral infarction of the
medial temporal lobe^.^^.^^ In addition, a unilateral left temporal lesion may be responsible for a
Korsakoff-like syndrome which may be temporary, lasting for hours or up to 6 months.i0*20*22
Agitated delirium. Patients with bilateral lesions in the distribution of the posterior cerebral
arteries occasionally appear agitated and hyperactive, a state resembling delirium tremens. I have
seen agitated delirium associated with bilateral
visual defects in several patients with established
posterior cerebral artery infarction, and in patients with an adverse reaction to vertebral angiography. In the patients with angiographic reactions, the vertebral, basilar, and posterior cerebral
arteries were widely patent and the agitated delirious s t a t e was accompanied by visual and memory defects. Within 24 hours, the entire syndrome
cleared, leaving amnesia which extended retrograde to the period prior to the angiography and
anterograde to the point of clearing.
Horenstein, Chamberlin, and ConomyZ6described nine patients with infarction of the undersurface of the temporal and occipital lobes whose
behavior included restlessness, agitation, forced
crying out and easy distractability with exaggerated responses to visual, auditory, or tactile
stimuli. The infarction involved calcarine,
fusiform, and lingual gyri in all patients and, in
some, the lesion extended to the medial hippocampal complex; in six patients, the lesions were unilateral and, in three, bilateral. Medina and ass o c i a t e ~also
~ ~ described
*~~
severe agitation in patients with visual field defects; the syndrome remitted within days to 2 months.
Motor and sensory defects. Sensory loss accompanying posterior cerebral artery territory infarction is often profound, with severe loss of touch,
position, a n d p a i n a p p r e c i a t i o n . Despite
somatosensory “deafferentation,” the patients
surprisingly retain ability to use the limbs and
frequently walk well. Objects are usually dropped
from the hand without the patient realizing the
loss. Loss of proprioception makes voluntary
movement variable; when strength is formally
tested, the patient may fail to perform the movement requested, or fail to exert power against resistance. If the examiner is patient and awaits the
desired movement, normal strength can often be
established. When the patient is asked to hold the
arm outstretched with eyes closed, the arm exhib-

January 1980 NEUROLOGY 30 77

iting sensory loss commonly rises or levitates in
contrast to the downward drift which accompanies
pyramidal system weakness. Some patients have
commented that the arm or leg seems to be “moving on its own,” and it is occasionally perceived as
dead or separate from the body. One patient with a
large posterior cerebral artery territory infarction
was surprised to learn that a blow to her face had
been delivered by her own hand, “unwilled” and
unrecognized.
Lesions limited to the ventroposterior-lateral
nucleus of the thalamus, as in pure sensory
stroke,46 usually cause “numbness” or paresthesias without important objectively demonstrable loss of perception. Lesions limited to the lateral
t h a l a m u s i n t h e d i s t r i b u t i o n of t h e
thalamogeniculate arteries cause unilateral limb
ataxia, clumsiness, and chorea, in addition to
variable sensory loss. The motor disorder is probably related to dysfunction of the ventral anterior
and ventrolateral nuclei and their connections
with efferents from the cerebellum a n d extrapyramidal systems.
Patients with lesions limited to the lateral
thalamus usually do not have the severe deafferentation seen in patients with a larger posterior
cerebral artery territory infarction or thalamic
hemorrhage, lesions t h a t i n t e r r u p t t h e
thalamoparietal radiations.
Motor paralysis is uncommon in patients with
occlusion of the posterior cerebral artery. These
patients usually retain their ability to make fine
distal movements, and do not usually have hyperreflexia, clonus, or extensor plantar reflexes.
However, facial weakness is common and may be
related to decreased tone of the facial muscles.
Occasional patients with involvement of the very
proximal posterior cerebral artery may have a n
infarction of the cerebral p e d ~ n c l e , ~so
’ that
hemiplegia accompanies the usual hemianopia
and hemisensory loss.

Discussion. This review has focused on the details
of the neurologic abnormalities of patients with
“top of the basilar” territory infarction. The locus
of brain dysfunction was corroborated by CT scans,
which showed radiolucent lesions in the medial
occipital or inferior temporal lobes (15 unilateral,
5 bilateral), or by autopsy (5). Unfortunately, in
our own series and in those described in the literature, the precise locus and mechanism of the vascular compromise is often uncertain. Most patients
have not had full angiography. At postmortem
examination, atherosclerosis of the vertebrobasilar system may be widespread, not allowing reconstruction of the exact pathophysiology of the infarction. Furthermore, an embolus present in life
often lyses or moves far distally by the time of
autopsy.
Foix and Hillemand4*discussed the anatomy of
78 NEUROLOGY 30 January 1980

small penetrating and circumferential branches of
the distal basilar artery. Segarra elaborated on
the anatomy of the perforating branches of the
mesencephalic artery (the proximal portion of the
posterior cerebral artery extending from the basilar bifurcation to the posterior communicating artery) and described two examples of infarction in
the distribution of this vessel. However, in neither
of Segarra’s cases was a lesion identified in this
vessel at postmortem. In his case 1,a right vertebral artery occlusion might have served as a nidus
for distal embolization, producing the sudden
onset of deficit. His case 2, another patient with a
syndrome of abrupt onset, had a heart murmur
and atrial fibrillation, but no lesion within the
vertebrobasilar arteries at postmortem. Sieben,
DeReuck, and Vander E e ~ k e reported
n~~
two patients with occlusion of the mesencephalic artery
documented at autopsy. Atherosclerosis with occlusion of small basilar branches remains a
hypothetical cause of high brainstem infarction,
but this has been documented only in branch disease of the lower basilar a r t e r ~ . ~ O * ~ l
The anatomic configuration of the basilar artery
with two arterial vessels merging into a larger
a r t e r y a n d t h e n b i f u r c a t i n g is u n i q u e .
Atherosclerosis is usually most severe at the origin of the vertebral artery in the neck, in the intracranial portion of the vertebral artery, and at
the proximal end of the basilar artery. Castaigne
and associates52 commented on the frequency of
embolic material within the distal basilar distribution. The basilar artery is widest a t its origin
and tapers distally; an embolus small enough to
traverse the vertebral artery would ordinarily not
block the basilar artery except distally. Intraarterial emboli arise from atherosclerotic plaques
in the carotid arte1y,5~35~
and atherosclerotic foci,
prominent in the proximal vertebral arteries,55
could serve as a source for distal emboli within the
vertebrobasilar system. In case 8 of Caplan and
R ~ s e n b a u m embolization
,~~
to the distal basilar
artery arose from a unilateral vertebral occlusion.
The sudden onset of stroke in our patients has led
us to postulate an embolic mechanism (intraarterial or cardiac) of the vascular occlusion, but
this was anatomically verifiable in only one case
(case 1).
Clarification of the clinical syndrome and safer
angiography may lead to further study and
analysis of the spectrum of possible underlying
vascular pathologies. Therapy will be possible
only when there is a more thorough understanding
of the vascular pathophysiology of the “top of the
basilar” syndrome.
References
1. Segarra JM: Cerebral vascular disease and behavior:1. The

syndrome of the mesencephalic artery. Arch Neurol
22~408-418,1970

2. Brust JCM, Behrens MM: “Release hallucinations” as the
major symptom of posterior cerebral artery occlusion: A
report of 2 cases. Ann Neurol 2:432-436, 1977
3. Caplan LR: Ptosis. J Neurol Neurosurg Psychiatry 37:l-7,
1974
4. Christoff N: A clinicopathological study of vertical eye
movements. Arch Neurol31:l-8, 1974
5. Collier J : Nuclear ophthalmoplegia with especial reference
to retraction of the lids and ptosis and to lesions of the
posterior commissure. Brain 50488-498, 1927
6. Fisher C M Some neuro-ophthalmological observations. J
Neurol Neurosurg Psychiatry 30:383-392, 1967
7. Growdon J , Winkler G, Wray S: Midbrain ptosis. Arch
Neurol 30:179-181, 1974
8. Halmagyi GM, Evans WA, Hallinan JM: Failure of downward gaze. Arch Neurol 35:22-26, 1978
9. Jacobs L, Anderson P, Bender M: The lesions producing
paralysis of downward but not upward gaze. Arch Neurol
28:319-323, 1973
10. Mohr JP,Leicester J., Stoddard L, e t al: Right hemianopia
with memory and color deficits i n circumscribed left posterior cerebral artery territory infarction. Neurology (Minneap) 21:1104-1113, 1971
11. Pasik P, Pasik T, Bender M: The pretectal syndrome in
monkeys: I. Disturbances of gaze and body posture. Brain
92521-534, 1969
12. Selhorst J , Hoyt W, Feinsod M, et al: Midbrain corectopia.
Arch Neurol 33:193-195, 1976
13. Seybold ME, Yoss RE, Hollenhorst RW, et al: Pupillary
abnormalities associated with tumors of the pineal region.
Neurology (Minneap) 21:232-237, 1971
14. Wilson SAK: Ectopia pupillae in certain mesencephalic
lesions. Brain 29524-536, 1906
15. Balint R: Seelenlrihmung des Schauens, optische Ataxie,
raumliche Storung der Aufmerksamkeit. Monatsschr
Psychiatr Neurol 25:51-81, 1909
16. Benson DR, Segarra JM, Albert ML: Visual agnosiaprosopagnosia. Arch Neurol 30:307-310, 1974
17. Reagan T, Trautmann J: Combined nuclear and supranuclear defects in ocular motility. Arch Neurol 35:133-137,
1978
18. Symonds C, MacKenzie I Bilateral loss of vision from cerebral infarction. Brain 80:415-454, 1957
19. Gassel M: Occipital lobe syndromes. In Vinken P, Bruyn G
(Editors): Handbook of Clinical Neurology. Amsterdam,
North Holland Publishing Co, 1969, vol 2, pp 640-679
20. Benson DF, Marsden CD, Meadows JC: The amnestic syndrome of posterior cerebral artery occlusion. Acta Neurol
h d 50:133-145, 1974
21. Alajouanine TH, Thurel R, Durupt L: h i o n protuberantielle basw d‘origine vasculaire e t hallucinose. Rev Neurol
(Paris) 7690-91, 1944
22. Caplan LR, Hedley-Whyte T Cuing and memory dysfunction in alexia without agraphia: A case report. Brain
97:251-262, 1974
23. Cohn R, N e u m a n n M, Wood D: Prosopagnosia: A
clinicopathological study. Ann Neurol 1:177-182, 1977
24. Facon E, Steriade M, Werthein N: Hypersomnie prolong&
engendr& par des Ibions bilatkrales du systeme activateur
medial: Le syndrome thrombotique de la bifurcation du
tronc basilaire. Rev Neurol (Paris) 98:117-133, 1958
25. Castaigne P, Buge A, Escourolle R, et al: Ramollissement
pdonculaire m d i a n , tegmento-thalamique avec ophtalmoplegie e t hypersomnie. Rev Neurol (Paris) 106:357-367,
1962
26. Horenstein S, Chamberlin W, Conomy J: Infarction of the
fusiform and calcarine regions: Agitated delirium and
hemianopia. Trans Am Neurol Assoc 92:357-367, 1962
27. Lhermitte J: Syndrome de la calotte du pdoncle cerebral:
Les troubles psycho-sensoriels d a n s les lesions du
m6socephale. Rev Neurol (Paris) 38:1359-1365, 1922
28. Medina J , Chokroverty S, Rubino F: The syndrome of agitated delirium and visual impairment: A manifestation of
medial temporo-occipital infarction. Neurology (Minneap)

26:355, 1976
29. Medina J , Rubino F, Ross E: Agitated delirium caused by
infarction of the hippocampal formation and fusiform and
lingual gyri. Neurology (Minneap) 24:1181-1183, 1974
30. Rubens AB, Benson DF: Associative visual agnosia. Arch
Neurol 24:305-316, 1971
31. van Bogaert L: Syndrome inferieur du noyau rouge, troubles psycho-sensoriels d‘origine mesocephalique. Rev
Neurol (Paris) 40:416423, 1924
32. van Bogaert L: L’hallucinose pdonculaire. Rev Neurol
(Paris) 43:608-617, 1927
33. Luria A R Human Brain and Pathological Processes. New
York, Harper and Row, 1966, pp 467-473
34. Victor M, Angevine J , Mancall E, e t al: Memory loss with
lesions of hippocampal formation: Report of a case with
some remarks on the anatomical basis of memory. Arch
Neurol 5:244-263, 1961
35. Fisher CM: Clinical syndromes i n cerebral hemorrhage. In
Fields WS (Editor): Pathogenesis and Treatment of Cerebrovascular Disease. Springfield, IL, Charles C Thomas,
Publisher, 1961, pp 318-338
36. Caplan L: Intracerebral hemorrhage. In Tyler HR, Dawson
D (Editors): Current Neurology, vol 11. Boston, Houghton
Miflin, 1979, pp 185-205
37. Gay AJ, Brodkey J, Miller JE: Convergence retraction nystagmus. Arch Ophthalmol 70:456-461, 1963
38. Jampel R, Fells P: Monocular elevation paresis caused by a
central nervous system lesion. Arch Ophthalmol80:45-57,
1968
39. Smith J, David N, Klintworth G: Skew deviation. Neurology (Minneap) 1496-105, 1964
40. Baruk H: Les hallucinations visuelles. Bull Mem Soc F r
Ophtalmol 2:713-739, 1936
41. Reeves AG, Plum F: Hyperphagia, rage and dementia, accompanying a ventromedial hypothalamic neoplasm. Arch
Neurol 20:616-624, 1969
42. Fisher-Perroudon C, Mouret J , Jouvet M: Sur un cas d’agrypnie (4 mois snas sommeil) a u cours d’une maladie de
Morvan: Effet favorable du 5-hydroxytryptophane. Electroencephalogr Clin Neurophysiol 36:1-18, 1974
43. Stuss D, Alexander M, Lieberman A, e t al: An extraordinary form of confabulation. Neurology 28:1166-1172.1978
44. Smith JL: Optokinetic Nystagmus. Springfield, IL, Charles
C Thomas, Publisher, 1963, pp 69-92
45. Hecaen H, De Ajuriaguerra J : Balint’s syndrome (psychic
paralysis of visual fixation) and its minor forms. Brain
77:373-400, 1954
46. Fisher CM: Pure sensory stroke involving face, arm and leg.
Neurology (Minneap) 15:76-80, 1965
47. Benson DF, Tomlinson EB: Hemiplegic syndrome of the
posterior cerebral artery. Stroke 2:559-564, 1971
48. Foix C, Hillemand P: Les arteres de l’axe encephalique
jusqu’au diencephale inclusivement. Rev Neurol (Paris)
41~705-739,1925
49. Sieben G, De Reuck J , Vander Eecken H: Thrombosis of the
mesencephalic artery. Acta Neurol Belg 77:151-162.1977
50. Fisher CM, Caplan LR: Basilar branch occlusion: A cause of
pontine infarction. Neurology (Minneap) 21:900-905,1971
51. Fisher C M Bilateral occlusion ofbasilar artery branches. J
Neurol Neurosurg Psychiatry 40:1182-1189, 1977
52. Castaigne P, Lhermitte F, Gautier JC, et al: Arterial occlusions in the vertebro-basilar system. Brain 96:133-154,
1973
53. Imparato A, Riles T, Gorstein F: The carotid bifurcation
plaque: Pathological findings associated with cerebral ischemia. Stroke 10:238-245, 1979
54.Moore W, Hale A: Ulcerated atheroma ofthe carotid artery.
Am J Surg 116:237-242, 1968
55. Hutchinson FC, Yates PO: The cervical portion of the vertebral artery-a clinicopathological study. Brain 79:319333,1956
56. Caplan LR, Rosenbaum AE: Role of cerebral angiography
in vertebro-basilar occlusive disease. J Neurol Neurosurg
Psychiatry 38:601-612, 1975

January 1960 NEUROLOGY 30 79

''Top of the basilar'' syndrome
Louis R. Caplan
Neurology 1980;30;72
DOI 10.1212/WNL.30.1.72
This information is current as of January 1, 1980
Updated Information &
Services

including high resolution figures, can be found at:
http://www.neurology.org/content/30/1/72.full.html

Citations

This article has been cited by 32 HighWire-hosted articles:
http://www.neurology.org/content/30/1/72.full.html##otherar
ticles

Permissions & Licensing

Information about reproducing this article in parts
(figures,tables) or in its entirety can be found online at:
http://www.neurology.org/misc/about.xhtml#permissions

Reprints

Information about ordering reprints can be found online:
http://www.neurology.org/misc/addir.xhtml#reprintsus