Nobuyuki Oka

Age associated axonal features in HNPP with 17p11.2 deletion in Japan

Objective: To clarify age related changes in the clinicopathological features of hereditary neuropathy with liability to pressure palsy (HNPP) in Japanese patients with deletion of 17p11.2, particularly concerning axonal abnormalities. Methods: Forty eight proband patients from 48 HNPP families were assessed as to clinical, electrophysiological, and histopathological features, including age associated changes beyond those in controls. Results: Motor conduction studies showed age associated deterioration of compound muscle action potentials in nerves vulnerable to repetitive compression (median, ulnar, and peroneal nerves), but not in others such as the tibial nerve. Sensory conduction studies revealed more profound reduction of action potentials than motor studies with little age related change. Large myelinated fibre loss was seen in the sural nerve irrespective of age at examination. Conclusions: Irreversible axonal damage may occur at entrapment sites in motor nerves in HNPP patients, progressing with aging. Sensory nerves may show more profound axonal abnormality, but without age association. The electrophysiological features of HNPP are presumed to be a mixture of abnormalities occurring from early in life and acquired features caused by repetitive insults at entrapment sites. Unlike Charcot-Marie-Tooth disease type 1A, age associated axonal damage may not occur unless the nerves are subjected to compression.

Clinical and electrophysiologic correlates of IVIg responsiveness in CIDP

To identify clinical and electrophysiologic features related to IV immunoglobulin (IVIg) responsiveness in chronic inflammatory demyelinating polyneuropathy (CIDP), the authors conducted a multicenter study on 312 patients with CIDP (199 responders and 113 nonresponders). Muscle atrophy and decreased compound muscle action potential were pronounced in nonresponders of IVIg. Male gender, longer disease duration, and slow progression of symptoms were also associated with IVIg unresponsiveness. Features suggesting axonal dysfunction in peripheral nerves indicated IVIg unresponsiveness in CIDP.

Mechanisms of tissue injury in vasculitic neuropathies

We studied the expression of candidate molecules for tissue injury in vasculitic neuropathies immunohistochemically, using samples obtained by nerve biopsy from seven patients with necrotizing angitis. In the involved vessels of all samples, numerous infiltrating cells were positive for perform, nitric oxide synthase (m-NOS), cyclooxygenase-2 (COX-2), or matrix metalloproteinase-1 (MMP-1). Cell-mediated cytotoxicity may be involved in the pathogenesis of small vessel injury in vasculitic neuropathies. In the endoneurium following axonal degeneration, scattered and phagocytosing macrophages showed immunostaining for m-NOS and MMP-1, but COX-2 was all but restricted to phagocytosing macrophages. This suggests a role for prostaglandins in nerve damage.

Tumor necrosis factor-α in peripheral nerve lesions

Abstract Immunocytochemical expression of tumor necrosis factor-α (TNF-α) was examined in nerve biopsy samples of patients with various disorders, focusing on nerve injury. TNF-α was mainly associated with phagocytosing macrophages in acute axonal injury, but the staining was more frequently seen in sections from patients with vasculitis than with metabolic neuropathy. Ramified macrophages outside nerve fibers were also positive for TNF-α in the acute stage of vasculitis. In active demyelinating lesions from patients with chronic inflammatory demyelinating neuropathy (CIDP), macrophages outside nerve fibers showed weak staining with TNF-α, but the cells adhering to myelinated nerve fibers showed definite staining. This may be due, in part, to the smouldering course of CIDP, and expression may be up-regulated transiently during the demyelinating process. These results indicate that macrophages, as the effector cells for both axonal injury and active demyelination, express TNF-α, but their activation mechanisms may vary among vasculitis, metabolic axonopathy and inflammatory demyelination.

Idiopathic thrombocytopenic purpura and mononeuropathy multiplex.

Peripheral neuropathy is an uncommon complication of idiopathic thrombocytopenic purpura (ITP). We report a 61-year-old man with ITP who developed acute-onset mononeuropathy multiplex. An electrophysiologic study revealed active axonal degenerative alteration, and a sural nerve biopsy showed axonal degeneration. Intraneural hemorrhage was suggested to be the most likely cause.