Facial nerve dysfunction in hereditary motor and sensory neuropathy type I and III

Abstract

Facial nerve function was studied in 19 patients with hereditary motor and sensory neuropathy type I (HMSN I) and 2 patients with hereditary motor and sensory neuropathy type III (HMSN III, Dé jé rineSottas), and compared to that in 24 patients with Guillain-Barré syndrome (GBS). The facial nerve was stimulated electrically at the stylomastoid fossa, and magnetically in its proximal intracanalicular segment. Additionally, the face-associated motor cortex was stimulated magnetically. The facial nerve motor neurography was abnormal in 17 of 19 HMSN I patients and in both HMSN III patients, revealing moderate to marked conduction slowing in both the extracranial and intracranial nerve segments, along with variable reductions of compound muscle action potential (CMAP) amplitudes. The facial nerve conduction slowing paralleled that of limb nerves, but was not associated with clinical dysfunction of facial muscles, because none of the HMSN I patients had facial palsy. Conduction slowing was most severe in the HMSN III patients, but only slight facial weakness was present. In GBS, conduction slowing was less marked, but facial weakness exceeded that in HMSN patients in all cases. We conclude that involvement of the facial nerve is common in HMSN I and HMSN III. It affects the intra-and extracranial part of the facial nerve and is mostly subclinical. Hereditary motor and sensory neuropathy type I (HMSN I, Charcot-Marie-Tooth type 1) is a chronic neuropathy with onset in the first or second decade of life. 9,17,20 Muscle weakness and wasting usually begins in intrinsic foot muscles. Hand muscle involvement is usually found at a later stage, and cranial nerves are clinically spared. Hereditary motor and sensory neuropathy type III (HMSN III, Déjérine-Sottas disease) begins in childhood and is characterized by a more severe course. As in HSMN I, foot muscles are affected earlier than hand muscles, and cranial nerve involvement is rarely observed clinically. 26 Nerve conduction velocities are markedly slowed in HMSN I, and even more so in HMSN III. 13These conduction abnormalities have been characterized mainly for limb nerves, and there are only a few reports about dysfunction of cranial nerves in HMSN I. Facial nerve conduction studies concerned only the distal segment of the nerve 18 or were based on measurement of the blink reflex, 21,23,25 where the

Blink reflex role in algorithmic genetic testing of inherited polyneuropathies

“…12 Consistent with this observation was that the facial motor study commonly had prolonged latency in inherited demyelinating cases. 13 Normative data for blink reflex studies have been generated by different groups, with 13 ms being the upper limit of normal for the R1 response for individuals > age 2 years 14 and R2 being less useful due to much greater variability. 12,15 Here, we evaluated the use of blink reflex R1 latency to distinguish demyelinating from axonal inherited polyneuropathies through a study of blink reflex responses in genetically confirmed patients.…”