Case number: 44

Brown-eyed man

Author: Claire Sheldon, Jason Barton


71 year man with recent acute onset of diplopia and nystagmus.

He had suddenly developed imbalance with nausea and vomiting 2 weeks ago, and since then has had vertical diplopia on extreme left lateral gaze, which is improving. He feels dizzy with his eyes open and tends to fall to the right.

He has longstanding high blood pressure and atrial fibrillation, and is taking coumadin (which was recently increased), trandolapril, verapamil, metoprolol, amlodipine, and simvastatin.

Acuity, pupils, fields and fundi are normal.
Ductions are full. Fixation is steady. Pursuit and VOR cancellation are reduced in all directions. Saccades are normal.
Cover test shows a small left hypertropia in primary position, left gaze and downgaze.

He has clumsiness of the left hand and leg, with dysdiadocokinesia of the left arm. On Romberg testing he leans to the left with eyes closed. Tandem gait is impaired.

The video shows his nystagmus in eccentric gaze:

Question: What is the type of nystagmus shown and where is the lesion?

View Diagnosis

Brun’s nystagmus, from a left cerebellopontine angle lesion.

CT showed a left cerebellar hemorrhage with edema and mass effect upon the junction of the medulla, pons and cerebellum:

 case44MR1  case44MR2

In the video, when the patient looks to the left, there is a coarse horizontal gaze-evoked jerk nystagmus (similar to the upbeat nystagmus in upgaze), and in right gaze, a finer horizontal vestibular jerk nystagmus of smaller amplitude.

This type of nystagmus indicates a lesion at the cerebello-pontine angle (CPA). The majority of patients with CPA tumors exhibit only unilateral vestibular nystagmus seen on contralateral gaze (with incidence rates varying between 10 and 75%). In Bruns’ nystagmus, there is also a gaze-evoked nystagmus, from failure of neural integration of horizontal position, due to damage to floccular-brainstem circuits, from significant brainstem distortion or compression.

In a retrospective study of 115 consecutive patients with CPA tumours, 16% had Brun’s nystagmus. In all of these patients, tumour size was > 3 cm and, in the majority of cases (89%), there was fourth ventrical displacement (Croxson et al., 1988).

Bruns’ nystagmus is often associated with optokinetic disturbances, cerebellar ataxia, additional cranial neuropathies, and signs of increased intracranial pressure (Katoh et al., 2007). This patient had impaired VOR cancellation (consistent with floccular dysfunction), limb and gait ataxia and an incomitant skew deviation.

REFERENCES:

  1. Croxson GR., Moffat DA., Baguley D. (1988) Bruns bidirectional nystagmus in cerebellopontine angle tumors. Clinical Otolaryngology 13: 153-157.
  2. Katoh, M., Aida, T., Imamura H., Aoki T., Yoshino M., Kashiwazaki, D., Takei H. (2007) Calcified vestibular schwannoma in the cerebellopontine angle. Journal of Clinical Neuroscience 12: 1207-1209.