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Myoclonus is a sudden, shock-like, involuntary movement caused by abnormal neuronal discharges. It may be cortical, subcortical, or spinal (segmental or propriospinal).1 One or a few contiguous spinal segments are involved in segmental myoclonus, while several segments are involved in propriospinal myoclonus since electrical activity spreads upwards and downwards from a spinal generator via propriospinal pathways. Propriospinal myoclonus may be caused by different spinal cord diseases or by drugs.1,2 Paraneoplastic neurological syndromes are rare immune mediated disorders associated with several types of cancer. Their pathophysiology is incompletely understood, although it is thought that specific antibodies formed against tumours may cross react with nerve cells.
A 49 year old woman presented with a 9 month history of involuntary, shock-like trunk and leg movements, occurring several times per day. Sporadically, they became prolonged, involved arm muscles, and caused transient respiratory failure. Several unsuccessful therapies included clonazepam, valproate, and gabapentin.
On examination, her gait was wide based, because of fear of falling due to jerks. Tone was normal. Spontaneous sudden, brisk contractions with trunk and lower limb extension were observed. The contractions were also elicited by postural changes and sensory stimuli such as tapping for evoking reflexes. During her hospital stay, the patient daily experienced these myoclonic phenomena with isolated jerks or flurries of repetitive jerks, involving the trunk, legs, and occasionally the arms. Infrequently, they progressed into sustained and prolonged tonic contractions also involving respiratory muscles with acute respiratory failure. Resuscitation was required …