Bruns nystagmus: an important clinical clue for cerebellopontine angle tumours.

Accepted 18 December 2017 DesCripTion A 24-year-old woman presented with gradual-onset left-sided hearing loss, progressive diminution of vision, headache and unsteadiness of gait. Comprehensive clinical evaluation revealed a left-sided lower motor neuron type of facial nerve palsy (figure 1), bilateral papilloedema, sensory loss in the distribution of ophthalmic branch of the left trigeminal nerve and cerebellar ataxia. Sensorineural hearing loss and absent corneal reflex were also observed on the left side. A coarse, left-beating nystagmus with leftward gaze and a fine primary-position rightbeating nystagmus which increased on rightward gaze, consistent with Bruns nystagmus (video 1), were appreciated. In view of the clinical findings, a diagnosis of a space-occupying lesion involving the left cerebellopontine angle was considered. MRI of the brain documented a space-occupying lesion (4×3.5 cm) in the left cerebellopontine angle, most likely a vestibular schwannoma (figures 2 and 3). The condition was explained to the patient and the need for surgical intervention. However, on being informed of the relative inexperience of neurosurgical interventions in such cases at our centre, she chose to attend a different medical facility with a higher surgical expertise, and was subsequently lost to follow-up. Bruns nystagmus is usually associated with large tumours of the cerebellopontine angle causing significant brainstem distortion, compression of the flocculus and/or vestibulocerebellum. In a study conducted on patients with unilateral vestibular schwannoma, the overall prevalence of Bruns nystagmus was estimated to be 11%. With large tumours having maximal diameter greater than 3.5 cm, the prevalence was observed to be higher (92% of patients had nystagmus, 67% of whom had Bruns nystagmus). It comprises of a coarse, high-amplitude horizontal nystagmus with low oscillatory frequency as the patient looks towards the side of the lesion, but a fine, low-amplitude, high-frequency primary-position nystagmus that increases as the patient looks to the side opposite the lesion. Bruns nystagmus primarily is a form of jerk nystagmus, characterised by alternating slow and fast components. After focusing an object on the fovea, failure of gaze-holding results in the deviation of the eyes, contributing to the slow component of the nystagmus. Subsequently, corrective saccades, in an effort to refocus the object of interest back on the fovea, contribute to the fast