Ocular neuromyotonia in a case of Paget's disease of bone

Abstract

The authors report a case of Paget's disease of bone and ocular neuromyotonia (ONM) in a 72-year-old woman. As far as we are aware, this association has never been previously described. The patient had an acquired left third cranial nerve palsy with oculomotor synkinesis and a left sixth cranial nerve palsy. Subjectively, she complained of recurring episodes of transient horizontal and vertical diplopia, lasting for about 30-40 sec and accompanied with discomfort in the left eye (LE). During those episodes, which occurred spontaneously or after sustained eccentric gaze, the LE became more esotropic with increasing restriction of abduction or hypotropic with increasing restriction of elevation. Electromyography (EMG) of the left medial rectus detected repetitive bursts of motor unit potentials with aspect of 'multiplets'. The oculomotor findings and the neurophysiological data evoked the diagnosis of ocular neuromyotonia which was subsequently confirmed by the effective response to carbamazepine. The patient had no history of radiation therapy, a frequent association of ONM. Cerebral and orbital CT scan showed a severe remodelling of the base of the skull. We suggest that cranial nerve palsies as clinically present in this patient, even if not neuroradiologically demonstrable, may result from bone thickening, especially the sphenoid and petrous bones. It is well-established that bone remodelling in Paget's disease may induce a local vascular 'steal phenomenon' which is known to cause neurological symptoms. Both mechanisms may be responsible for ONM.

Key Words:

• Key words Paget' s disease
• ocular neuromyotonia
• ocular electromyography