Abstract & Commentary
By Michael Rubin, MD, Professor of Clinical Neurology, NewYork-Presbyterian, Hospital, Cornell Campus. Dr. Rubin is on the speaker's bureau for Athena Diagnostics, and does research for Pfizer and Merck.
Synopsis: Most polyneuropathies in teenagers are due to hereditary demyelinating or metabolic disorders.
Source: Kararizou E, et al. Polyneuropathies in Teenagers: A Clinicopathological Study of 45 Cases. Neuromuscular Disord. 2006;16:304-307.
What are the most common forms of polyneuropathy in teenagers? To address this question, a retrospective review of patients' records ages 13-19 years, referred for nerve biopsy to the Neuropathology Department of Athens University over a 20-year period, was undertaken. Forty-five patients, 32 boys and 13 girls, were included. All had undergone neurological examination, including muscle strength testing, sensory examination, deep tendon reflex evaluation, blood studies encompassing routine biochemistry, hematology, and serology, cerebrospinal fluid analysis, electrodiagnostic studies comprising nerve conduction studies and needle electromyography, and sural nerve biopsy with teased fiber and electron microscopic evaluation. Clinical, electrophysiological, and pathological findings were used to categorize patients into axonal, demyelinating, or mixed axonal and demyelinating polyneuropathy groups.
Based on clinical and electrophysiological data, 38 patients had distal symmetric sensorimotor polyneuropathy, 3 had symmetric sensory polyneuropathy, and 2 each had asymmetric sensorimotor polyneuropathy or mononeuropathy multiplex. Biopsy revealed demyelination in 38 and axonal loss in 7, with endoneurial inflammatory infiltrates in 6 and epineural and perineural infiltrates or positive human polyclonal antibody to C3 and fibrinogen in 2 each. Overall, 28 patients (62.2%) were diagnosed with hereditary neuropathy, encompassing hereditary motor and sensory (Charcot-Marie-Tooth) type-I (n = 11, 24.4% overall), type-II (n = 6, 13.3% overall), and type-III (n = 2, 0.04% overall), Friedreich ataxia (n = 6, 13.3% overall), hereditary neuropathy with liability to pressure palsy, Roussy-Levy syndrome, or hereditary sensory neuropathy type-I (1 each, 0.02% overall). Nine (20%) demonstrated chronic inflammatory demyelinating polyneuropathy (CIDP), 4 (8.8%) suffered from a hereditary metabolic disorder, including metachromatic leukodystrophy, adrenoleukodystrophy, porphyria, or Fabry disease, and 2 each (4.4%) had toxic or vasculitic neuropathy. As opposed to adults, but similar to children, hereditary neuropathy comprises a large proportion of teenager polyneuropathy. CIDP is twice as common in teenagers, as compared to children, but other causes have a similar incidence throughout the first 2 decades of life.
Nerve biopsy can assist in the identification of teenage and childhood polyneuropathy. Yet, electrophysiologic studies remain the cornerstone of evaluation, providing a rational approach to timely and correct diagnosis. Among 74 children with polyneuropathy, nerve conduction studies categorized patients into 5 groups (Polat M, et al. Pediatr Neurol. 2006;35;11-17). Acute, axonal polyneuropathy was seen in 32 (43%), chronic axonal polyneuropathy in 16 (22%), demyelinating motor and sensory polyneuropathy in 13 (17%), pure sensory polyneuropathy in 11 (15%), and high-low syndrome (a newly defined electrodiagnostic pattern with peripheral nerves relatively unresponsive even to stimuli of long duration and high voltage, motor amplitudes low, prolonged latencies, slowed motor velocities, absent sensory responses, and normal needle electromyography) in 2 (3%). Precise etiologic diagnosis was possible in all children with acute axonal polyneuropathy, pure sensory polyneuropathy, and high-low syndrome. No etiology was found in 5 (31%) chronic axonal and 3 (23%) demyelinating motor and sensory polyneuropathy cases. Diabetes was the most common cause (n = 9, 82%) of pure sensory polyneuropathy. Toxic neuropathy comprised 56% (n = 18) of acute axonal polyneuropathy, caused by vincristine (n = 9), glue sniffing (n = 7) or organophosphate poisoning (n = 2). Nerve conduction studies and EMG should be considered an extension of the physical examination, and will prove cost-effective when performed as part of the evaluation of children with polyneuropathy.