Focal hand dystonia after cervical whiplash injury.

There is currently a general consensus of agreement that dystonia is a disease of the basal ganglia, although dystonic symptoms have been observed in association with lesions in various different sites of the sensory and motor pathways. 1 In particular, cervical in-tramedullary lesions have been reported as being a rare cause of focal hand dystonia, 2 although in these cases the pathogenesis of the movement disorder remains unclear. To help clarify this point, we report the case of a patient who developed dystonic features of the right hand after a cervical whiplash injury. A 44 year old man developed sensory alterations and impairment of strength in the right hand immediately after a whiplash injury. Neurological examination showed proprio-ceptive and tactile anaesthesia of the first three fingers of the right hand, mild hy-pasthenia on grasping, and adiadochokinesis of the right upper limb. Tendon reflexes, muscle tone, and plantar responses were normal, and thorough neurological examination of the upper left limb and lower limbs also yielded normal findings. Cervical magnetic resonance imaging (MRI) revealed a small right posterior C5-C6 lesion of the spinal cord (see fig 1). Brain MRI, nerve conduction studies , EMG, and transcranial magnetic stimulation were all normal. Two months later, the patient developed writhing movements of the first three fingers and a dystonic posture of the right hand, worsened by movement, and more evident when the eyes were closed. Ability to write, use a knife or fork, and hold a glass were moderately impaired, especially without visual guidance. Neurological examination at this time revealed slight cutaneous and proprioceptive hypaesthesia and paraes-thesias of the first three fingers of the right hand, while grasping strength was normal and the EMG recording showed a pattern of co-contraction of the forearm flexor and extensor muscles. Median nerve sensory evoked potentials (SEPs) revealed normal peripheral and central conduction times, but spinal and cortical waves were larger in response to stimulation of the affected side. In particular, the cervical potential showed a right:left ratio of 1.2, while the right:left ratio for the cortical waves ranged from 1.8 to 2.4. The patient had no history of neuroleptic intake. This is the first report of hand athetosis-dystonia after a cervical whiplash injury to the spinal cord. We are reasonably confident that the lesion was secondary to the trauma, rather than representing inflammation, because the symptoms appeared immediately after the whiplash injury and in view of the …