"Numb, clumsy hands" and tactile agnosia secondary to high cervical spondylotic myelopathy: a clinical and electrophysiological correlation.

Four patients presented with a distinctive syndrome of "numb, clumsy hand" and tactile agnosia. Myelography and computed tomographic myelography (CTM) of the cervical spine documented major spondylotic compressive lesions mainly between the C3 and C5 levels. The cortical responses of dermatomal somatosensory evoked potentials (DSEPs) revealed progressively prolonged peak latencies and progressively decreased amplitudes of early components from C6 to C8 dermatomal stimulation. In comparison, the C5 and L2 DSEPs were affected to a lesser extent. This finding suggests that high cervical cord compression may produce dysfunction of the dorsal column caudal to the direct compressive sites. In other words, the funiculus cuneatus of C6-8 cord is most affected in high cervical myelopathy. Moreover, the funiculus cuneatus is within the border zone susceptible to an overall reduction in blood flow. We conclude therefore, that ischemia secondary to cord compression is the pathophysiology resulting in this unique syndrome of "numb, clumsy hands" and tactile agnosia.