Clinical Neurology and Neurosurgery 99 (1997) 282 – 286

Case report

Cortical blindness
J.E. Dalman a, W.I.M. Verhagen a,*, P.L.M. Huygen b
a

Department of Neurology, Canisius-Wilhelmina Hospital, PO Box 9015, 6500 GS Nijmegen, Netherlands
b
Department of Otolaryngology, Uni6ersity Hospital Nijmegen, Nijmegen, Netherlands
Received 1 May 1997; received in revised form 1 September 1997; accepted 11 September 1997

Abstract
A 79-year-old woman with persistent cortical blindness caused by bilateral temporo-occipital infarctions was followed for 8
months. She had no light or visual motion perception. Our patient’s visual imagery was intact, which was demonstrated when
drawing elementary shapes; however, her drawing of objects was poor. Optokinetic nystagmus could not be elicited, but the
vestibulo-ocular reflex (VOR) seemed intact. Although she was able to suppress her VOR by ‘fixating’ her outstretched hand
which moved in phase with her head and body, she showed saccadic tracking eye movements in an attempt to visually ‘follow’
the self-generated movements of her outstretched hand, while her body and head were stationary. Such saccadic tracking seemed
to be different from the previously described smooth tracking of self-moved targets by patients with acquired blindness caused by
anterior visual pathway dysfunction. © 1997 Elsevier Science B.V.
Keywords: Posterior cerebral artery; Optokinetic nystagmus; Fixation suppression; Brain infarction; Visual imagery

1. Introduction
Complete cortical blindness, which is caused by lesions affecting the geniculostriate pathways, is an uncommon neurological disorder and is rarely persistent.
We had the opportunity to examine a patient with
complete cortical blindness that proved to be persistent.

2. Case report (patient, methods and results)
A 79-year-old right-handed woman was admitted to
our hospital with acute complete loss of vision. She had
no headaches, nausea or other complaints. Her medical
history included successful cataract extraction from the
right eye 2 years previously, diabetes mellitus, hypertension and recurrent cerebral infarctions. Twenty-one

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years previously, she had suffered an ischaemic stroke
in the right temporal and occipital lobes, which caused
left homonymous hemianopsia. She had a second ischaemic stroke 14 years later. Left temporo-central
cerebral infarction resulted in right-sided hemiparesis
and dysarthria, but she recovered almost completely.
Four years later she had another stroke in the right
cerebral hemisphere. A cerebral CT scan at that time
showed infarctions in the right cerebral hemisphere in
the territories of the anterior, middle and posterior
cerebral arteries.
On admission, our patient was confused, restless and
disorientated in time. There was a conjugate deviation
of the eyes to the left. Vision seemed to be absent,
although she denied being blind and had visual confabulations. Her pupillary light reflexes were normal, but
pursuit eye movements could not be elicited. Cranial
nerve functions were otherwise normal. On the left side
she had moderate spastic hemiparesis, exaggerated muscle tendon reflexes and an extensor plantar reflex. Our

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Fig. 1. Brain CT revealed infarctions in the right frontal lobe and in both temporo-occipital lobes.

clinical diagnosis was cortical blindness, probably
caused by several, successive cerebral infarctions.
Electro-encephalography showed severe abnormalities over the right cerebral hemisphere. The posterior
dominant rhythm was 5 – 7 Hz on both sides. There was
no reaction to photostimulation.

Cerebral CT scans showed bilateral brain infarctions
that involved the cuneus on both sides and precuneus
on the left side, the lateral occipital gyrus on the right
side, the medial and lateral occipitotemporal gyrus,
hippocampus and parahippocampal gyrus on the left
side, as well as the superior frontal gyrus, cingulum

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J.E. Dalman et al. / Clinical Neurology and Neurosurgery 99 (1997) 282–286

Fig. 2. Eye movement recording of the patient attempting to smoothly track the thumb of her sinusoidally moving outstretched right arm; note
the saccades.

gyrus, medial and superior temporal gyrus, supramarginal gyrus, inferior frontal gyrus and angular gyrus
occipital on the right side (Fig. 1). Brain MRI was
inconclusive because of movement artifacts.
Her optokinetic and vestibular responses were evaluated 6 weeks and 4 months after the onset of cortical
blindness. We attempted to calibrate eye movements by
letting the patient direct her eyes towards her outstretched hands, while the examiner held her hands so
that these subtended an angle of about 20° and touched
her index fingers in alternation. She made fairly reproducible saccades, but these overshot the target, which
rendered exact measurements impractible. We attempted to elicit optokinetic nystagmus (OKN) responses, using monocular or binocular stimulation
(stimulus shadow stripes on a video monitor screen
covering 32× 24° in front of the patient) at a velocity
of 30°/s (left/right or upward/downward), or during
whole body rotation at a constant speed of 40°/s in full
light with the eyes open. No OKN could be elicited in
either direction and the patient denied seeing any movement.
Although she was able to suppress her VOR by
‘fixating’ her outstretched hand, which moved in phase
with her head and body, [1] she showed saccadic tracking eye movements in an attempt to visually ‘follow’ the
self-generated movements of her outstretched hand
while her body and head were stationary (Fig. 2). Such
saccadic tracking seemed to be different from the previously described smooth tracking of self-moved targets
in patients with acquired blindness caused by anterior
visual pathway dysfunction [1].
The vestibulo-ocular reflex (VOR) was tested with
voluntary head shaking, 90°/s velocity step tests and
sinusoidal stimulation (frequency 0.05 Hz, peak velocity
50°/s) in the dark and in the light with the eyes open.
Each of these tests elicited lively nystagmic responses,
but there were no tangible differences between those
obtained in full light or complete darkness. We were
unable to reliably measure the gain of the VOR, but the
responses seemed normal and the decay in nystagmus
slow phase velocity after velocity steps indicated a
normal time constant [2].

In order to assess different aspects of visual imagery,
we tested our patient on different imagery tasks including her drawing capacity, using Dutch test material
fairly similar to that described by Chatterjee et al. ([3]
for examples of the categories and the type of questions). She performed reasonably well on most items,
except for those requiring imagery of directions, angle
judgement and ‘colour odd-man-out’ (e.g. the question
’Which of the these three objects are similar in colour:
sunflower, cherry and blood?’). Drawing of objects (car,
butterfly, clock, house, flower) was very poor (Fig. 3).
Drawing of elementary shapes (square, rhomb, triangle
and circle) was fairly accurate.
During her period of hospitalization, the patient
showed clear immediate and recent memory dysfunction. She had left-right disorientation and remained
disorientated in time. Her restlessness improved with

Fig. 3. Drawings by the patient: (A) rhomb; (B) circle; (C) square; (D)
house; and (E) tree.

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time, but she lacked initiative. Learning abilities were
disturbed. Perseveration was evident during a drawing
assignment. She was able to perform various activities
of daily living, such as washing and dressing herself,
eating and drinking. Her vision did not improve during
the 4 months in hospital. She was subsequently transferred to a nursing home. There were no signs of
improvement 4 months later.

3. Discussion

3.1. General clinical features and prognosis
Cortical blindness (CB) refers to visual loss in the
presence of normal pupillary light reflexes, which is
caused by bilateral lesions of the visual pathways in the
temporo-occipital lobes. The most frequent cause of CB
is cerebral vascular disease. In the series described by
Aldrich et al. [4], CB had been caused by spontaneous
ischaemic stroke in 32%, while Symonds et al. mentioned 25% [5]. Other frequent causes are cardiac
surgery and cerebral angiography [4]. In addition to
blindness, patients usually show confusion, disorientation and they may have visual hallucinations. They may
deny their blindness (Anton’s symptom), especially if
they have complete visual loss and memory impairment
[4], are unable to acquire new knowledge and show
some degree of retrograde amnesia. Such memory impairments commonly result from bilateral hippocampal
damage. The posterior cerebral artery supplies the medial and basal parts of the temporal lobe including the
hippocampus. Usually, the memory disturbances are
caused by bilateral lesions, although Brierley mentioned
amnesia in unilateral basal temporal lesions [6].
Aldrich et al. found that the prognosis was poor in
patients with diabetes mellitus, hypertension, or associated cognitive, language or memory impairments. Patients with bi-occipital CT lesions never showed
complete recovery of vision. Prognosis also depended
on the cause of CB and proved to be much better in
patients with CB following surgery or cerebral angiography, than following a stroke [4].

3.2. Optokinetic nystagmus
Most patients with persistent complete CB have a
persistent lack of OKN responses [4,7 – 12]. As far as we
know, only Ter Braak et al. [12] mentioned partial
recovery of OKN owing to the possible re-appearance
of (diminished) stare OKN in one direction, with a slow
build-up of OKN response velocity and (shortlasting)
optokinetic after-nystagmus in the same direction.
However, although their patient had no spontaneous
nystagmus at the time of examination, he had shown
spontaneous left-beating nystagmus 1 month previously

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and therefore, the possibility of ‘arousal’ of spontaneous nystagmus cannot be excluded.

3.3. ‘Tracking’ /‘fixating’ the outstretched hand
Patients with acquired complete blindness caused by
a variety of anterior visual pathway lesions retain the
ability to generate smooth eye movements and suppress
the VOR by ‘tracking’ or ‘fixating’ their outstretched
hand [1]. Our patient was also able to suppress the
VOR, but unable to smoothly track the self-generated
movements of her outstretched hand; she showed saccadic tracking instead. The suppression of the VOR
seemed to be in line with good visual imagery and/or a
normal somatosensory system; normal subjects are also
able to suppress the VOR to a certain extent, probably
by the same mechanism. The self-generated saccadic
tracking movements demonstrated an intact somatotopic map and intact visual imagery. Steinbach [13]
mentioned similar responses with a prominent saccadic
component in normal subjects ‘tracking’ their own
moving hand in the dark. Our group observed fairly
similar responses in normal subjects who attempted to
‘track’ one of their knees during cervico-ocular reflex
(COR) stimulation, i.e. sinusoidal movement of the
body under the fixed head, eyes open in the dark [14].
Although in this respect, our patient behaved in a
similar way to normal subjects, it seems difficult to
explain why she apparently succeeded in suppressing
the VOR but failed to smoothly track her moving hand.
There would be no discrepancy if her VOR suppression
utilized a similar position-controlling system to her
tracking system and did not invoke any velocity control. The limited resolution of electronystagmography,
however, does not allow any clear distinction between
velocity-controlled and position-controlled VOR cancelling. The apparent discrepancy that a patient with
acquired complete blindness caused by anterior pathway pathology was able to smoothly track his outstretched hand [1], while normal subjects [13] and our
patient were unable to do so, may be explained by the
possibility that the blind patient with longstanding
anterior pathway impairment, but intact cortical function and visual imagery, had developed velocity-controlled,
i.e.
smooth
‘tracking’
by
utilizing
somatosensory information, similarly to the development of a smooth COR in monkeys [15] and
labyrinthine-defective subjects [14].

3.4. Visual imagery
Our patient’s performance on visual imagery tasks
seemed to confirm the conclusion of Chatterjee et al. [3]
and Goldenberg et al. [16] that the primary visual
cortex is not essential for visual imagery. Our data do
not support the suggestion made by Farah [17], that the

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posterior left quadrant of the brain in particular, is
implicated in the ability to generate images because our
patient had a clear lesion in that area, but performed
reasonably well on visual imagery tasks.

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