Ataxic vs painful form of paraneoplastic neuropathy

To characterize the clinicopathologic features of ataxic and painful forms of paraneoplastic neuropathy. Clinical, electrophysiologic, and histopathologic findings were assessed in 17 patients with paraneoplastic neuropathy. Clinical features can be categorized into two groups: one group (13 patients) with predominantly deep sensory disturbance and a second group (4 patients) with predominantly superficial sensory disturbance. The former group showed severe sensory ataxia and predominantly large myelinated fiber loss in the sural nerve. The latter group showed marked pain, in particular, severe mechanical hyperalgesia, and predominantly small myelinated and unmyelinated fiber loss. Nerve conduction assessment indicated an axonal neuropathy pattern in both groups, while sensory action potentials were more markedly diminished in the sensory ataxic form. Anti-Hu antibodies were detected in half of the patients in both groups. Treatment for cancer was effective to improve or stabilize neuropathic symptoms in some cases from both groups. Immunotherapy was effective only for a short time. Paraneoplastic neuropathy can be characterized into two groups by the presence of sensory ataxia or severe spontaneous pain and severe mechanical hyperalgesia. Preferential small myelinated and unmyelinated fiber loss correlated to the cases of severe pain.