Pure motor mononeuropathy with distal conduction block: an unusual presentation of multifocal motor neuropathy with conduction blocks.
OBJECTIVE
To report an hitherto undescribed presentation of Motor Neuropathy with Multifocal Conduction Block (MMNCB).


METHODS
Description of two patients presenting with complete paralysis of the 3 heads of the trapezius muscle (case one) and progressive weakness of finger extension (case 2).


RESULTS
Nerve conduction studies (NCS) established that the corresponding nerves were distally inexcitable. In the affected muscles, no voluntary activity was elicited in both patients with spontaneous activity noted in patient 2. Systematic NCSs documented an asymptomatic, partial conduction block (CB) in a median nerve forearm segment in both patients. Neurophysiological follow-up after a dramatic response to intravenous immunoglobulins demonstrated recovery of the initially unobtainable motor responses.


CONCLUSIONS
This indicates that a complete, distal CB of the motor fibers destined to the trapezius muscle in patient 1, and to the extensor indicis proprius in patient 2, had caused the heralding deficits.


CONCLUSIONS
These findings underscore the possibility of distal CB in this disorder and the need for extensive NCSs, including asymptomatic nerves, for an accurate diagnosis.
Vucic
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Department of Neurology, Bigelow 1256, Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114, USA.
Dawson
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Sun
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Cros
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D000328:Adult; D005260:Female; D005385:Fingers / Q000502:physiology; D005542:Forearm / Q000294:innervation / Q000502:physiology; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use; D007167:Immunotherapy; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D009046:Motor Neurons / Q000473:pathology*; D018908:Muscle Weakness / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology*; D009460:Neurologic Examination; D009468:Neuromuscular Diseases / Q000503:physiopathology*; D010243:Paralysis / Q000503:physiopathology
D016756:Immunoglobulins, Intravenous