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

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J Neurol Neurosurg Psychiatry. 2005 Aug;76(8):1109-14. MENTIONS CMT.

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

Koike H, Hirayama M, Yamamoto M, Ito H, Hattori N, Umehara F, Arimura

K, Ikeda S, Ando Y, Nakazato M, Kaji R, Hayasaka K, Nakagawa M,

Sakoda S, Matsumura K, Onodera O, Baba M, Yasuda H, Saito T, Kira J,

Nakashima K, Oka N, Sobue G.

Department of Neurology, Nagoya University Graduate School of

Medicine, Nagoya 466-8550, 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.