SHORT COMMUNICATION

Acta Neurol Scand., 1986:73:444-446
Key words: locked-in syndrome;ocular bobbing.

Locked-in syndrome associated with ocular bobbing
C. C. Tijssen, J. P. Ter Bruggen
Department of Neurology, St. Elisabeth and Maria
Hospitals, Tilburg, The Netherlands

ABSTRACT - Locked-in syndrome together with an ocular bobbing phenomenon was observed in a 41-year-old man, an association which has not been reported earlier. Computerized tomography demonstrated an infarction of the medio-ventral portion of the pons. The
patient survived and is still alive ten months after the onset of the disease with severe neurological deficit.
Accepted for publication October 9, 1985.

The locked-in syndrome (LIS) is a rare clinical condition consisting of paralysis of all four extremities and
the lower cranial nerves without interference with consciousness. The only remaining voluntary movements
are blinks of the eyelid, which allow the patient to communicate, and vertical eye movements (1,2). Most
cases are caused by a large ventral infarction of the
pontine base.
Ocular bobbing is a distinctive abnormality of eye
movements characterized by abrupt, spontaneous,
usually conjugate, downward jerks of both eyes followed by a slow return to the midposition. There is
paralysis of spontaneous and reflex eye movements in
the horizontal plane. The patient may be comatose, obtunded or fully conscious (1,3). The syndrome has
been most often associated with extensive destructive
lesions of the pons. It can also occasionally occur in
pontine dysfunction resulting from brainstem compression and metabolic encephalopathy (43).
We describe a patient with (LIS) caused by an infarction of the brainstem, who also showed the phenomenon of typical ocular bobbing, an association which
has not been reported earlier.

Case report
A 41-year-old man was admitted to hospital with
symptoms of acute headaches, facial numbness, disturbances of speech and difficulty in walking. He had
noticed a right facial paresis and a right hemiparesis.
Three weeks earlier he had experienced the same complaints which had disappeared spontaneously within a
few hours. There was a history of mild hypertension.

On examination he was conscious and had a blood
pressure of 200/ 120. His speech was dysarthric and he
had a conjugate deviation of gaze to the right. There
was a right hemiparesis and hemihypaesthesia. Deep
tendon reflexes were elevated on the right with a positive Babinski sign. In the first days following admission
his condition deteriorated seriously with temporary
Cheyne-Stokes breathing. He developed bilateral hemiplegia. His pupils were miotic but reactive to light.
The corneal reflexes were absent. The patient remained
conscious and was able to blink his eyelids. No other
voluntary movements were possible. His eyes showed a
typical ocular bobbing with spontaneous downward
jerking and slow return to the mid-position. This was
measured by oculographic recording (Fig. 1). Horizontal eye movements were not possible, with absent oculovestibular responses. Nor did they occur on caloric
stimulation.
The EEG repeatedly showed no abnormalities. The
cerebrospinal fluid showed 35/3 cells/mm3 and an elevated total protein of 0.82 g/l (normal until 0.50). CT
scan on the day of admission was normal. A repeat CT
scan, three weeks later, showed an infarction in the medio-ventral part of the pons with extension somewhat
more to the left than to the right (Fig. 2). Registration
of the blink reflex with electrical stimulation of the supra-orbital nerve showed first responses with normal latencies. The second responses were absent on both
sides. The brainstem auditory evoked potentials
(BAEP) revealed wave I and I1 with normal latencies
on right and left stimulation. Wave 111 to V could not
be elicited. The short latency somatosensory evoked
potentials (SSEP) showed a normale wave pattern (P9,

LIS AND OCULAR BOBBING

Fig. 1. Oculographic recording of the ocular bobbing
phenomenon of the patient showing the abrupt, arrhythmic, conjugate downward jerks of both eyes followed by a slow return to the midposition (AC amplifier, time constant 10 S)
t: downward movement of the eyes from mid-position.
1: upward movement of the eyes to mid-position.

N11, N13/P13, P14, N19, P22) on stimulation of the
left median nerve. On stimulation of the right median
nerve the P14, N19 and P22, could not be elicited.
The patient was treated with anticoagulant therapy,
regulation of blood pressure, tracheostoma, gastrostoma and suprapubical urinary drainage. Eight weeks after admission the condition had stabilized and the following months a slight improvement of the neurological findings occurred. The patient was able to communicate by blinking his eyelids. The ocular bobbing
phenomenon persisted for two months and then gradually disappeared. Intermittent oral automatisms consisting of sucking and chewing movements were present and could be evoked by noxious stimuli. There
was a slight voluntary movement of the head, but
otherwise quadriplegia persisted. In this state the patient was referred to a nursing home, six months after
admission. Four months later he was still alive and
there was no significant change in his neurological condition.

445

The vertical eye movements are generally described
as normal in patients with LIS, due to sparing of the
tegmental corticobulbar tracts that innervate the third
nerve nuclei (1). A dissociated loss of vertical eye
movements with slowed saccades and normal pursuit
movements has also however been found in a patient
with LIS (7). Our patient demonstrated a typical ocular
bobbing phenomenon in combination with LIS. This
was caused by a large infarction of the medio-ventral
part of the pons as demonstrated by computerized
tomography. Ocular bobbing is most frequently seen in
severe destructive caudal pontine lesions, the result of
either infarction or hemorrhage (43). The pathophysiologic mechanism underlying this eye movement remains obscure (3). It has been postulated that the
phenomenon is caused by selective involvement of the
pathways for horizontal gaze while more rostra1 input
for vertical gaze is retained (9). Others, however, have
attributed it to neural activity originating in the intact
medulla and suggest that bobbing is the result of normal pathways for downgaze (10). The clinical symptoms and the absence of the second responses of the
blink reflex in our patient are in favour of the first hypothesis.
Studies of evoked potentials have been rarely reported in patients with LIS and ocular bobbing. Different findings of BAEP’s have been described in patients
with LIS; these can be normal or show abnormalitiesof
wave IV and V (8). Our patient had normal peak latencies of wave I and I1 but the other wave forms could
not be elicited, indicating that the brainstem damage
extended beyond the pontine base and included the

Discussion
The LIS syndrome results from disruption of the corticospinal tract and the corticobulbar fibres to the lower
cranial nerve nuclei (1,2). The blink reflex of our patient elicited by stimulation of the supra-orbital nerve
showed a first response with normal latencies on both
sides, indicating that the facial nuclei were intact. The
presence of oral automatisms which could be evoked
by noxious stimulation suggests that the bulbar system
of mastication was also intact (6).

Fig. 2. (3scan of the patient showing a large infarction of the medio-ventral part of the pons.

446

C. C. TIJSSEN AND J.P. TER BRUGGEN

pontine tegmen (11). The SSEPs demonstrated a disturbance at the level of the left medial lemniscus on stimulation of the right median nerve corresponding to
the initial right hemi-hypaesthesia (12); the SSEPs on
stimulation of the left median nerve were completely
normal.
The prognosis of both LIS and ocular bobbing of
vascular origin is poor, most patients dying within a
few weeks of onset (1,2,3). Our patient however survived and is still alive ten months later with severe neurological deficit.

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Address
C. C. Tijssessen, M.D.
Department of Neurology
St. Elisabeth and Maria Hospital
P.O. Box 90151
5000 LC Tilburg
The Netherlands