Synchronised Paroxysmal Ocular Tilt Reaction and Limb Dystonia

ABSTRACT

A case of paroxysmal ocular tilt reaction due to a midbrain cavernoma showing co-existing limb dystonia is described with particular reference to the synchronisation of eye and limb paroxysms. The single case has been observed over a 20-year period with video documentation of eye and limb movements. The function of the relevant neuro-anatomical circuits have been investigated. The now 51-year-old female patient suffered from a right midbrain haemorrhage 20 years earlier. She developed a synchronized paroxysmal ocular tilt reaction and focal limb dystonia, associated with a unilateral startle-like response. Video-oculography and electromyography during paroxysms demonstrated left forearm electromyography spikes time locked with bursts of ocular torsion. Whilst the ocular tilt reaction may be explained by a single irritative lesion of the right interstitial nucleus of Cajal, additional involvement of the right rostral interstitial nucleus of the medial longitudinal fasciculus was suggested by abnormal binocular scleral coil recordings of the torsional vestibulo ocular response. There was a marked unilateral acoustic startle-like response, not explained by damage to either nucleus. Treatment with acetazolamide abolished the attacks. The observations suggest that the coexistence of skew deviation, conjugate ocular torsion and limb dystonia in meso-diencephalic lesions may occur because neural centres controlling these eye and limb movements are closely related anatomically, rather than through the activation of a “hard wired” physiological synkinesis. We propose that the paroxysms are generated within the zona incerta where excitatory auditory, somatosensory and motor neurons are densely packed and extensively project to centres of gaze and motor control.

Keywords: :

• Ocular tilt reaction
• hemi-dystonia
• myoclonus
• acetazolamide
• startle response
• zona incerta