Compressive myelopathy at the cranio-cervical junction is a complication of mucopolysaccharidoses
(MPS). To detect cervical myelopathy we recorded median and posterior tibial nerve
SEPs in 15 patients aged 2.4 - 33.4 years (median 8.8 years) with MPS I-S (n = 3),
MPS IVA (n = 8) and MPS VI (n = 4). In addition to the cortical waveforms we recorded
the subcortical median nerve SEPs N13b and P13 generated near the cranio-cervical
junction and the lemniscal P30 after posterior tibial nerve stimulation. MRI studies
in 13 subjects revealed spinal cord compression at the cranio-cervical junction in
10 patients; 5 patients had an increased signal intensity on the T2-weighted initial MRI indicating high cervical myelomalacia and 4 patients had clinical
signs of cervical myelopathy. We did not find a relationship between the SEPs and
spinal cord compression. Abnormal SEPs were found in the patients with MRI evidence
of myelomalacia (sensitivity 1.0, specificity 1.0) and correspondingly in the patients
with clinical signs (sensitivity 1.0, specificity 0.91). The SEPs consequently deteriorated
in 2 subjects of 7.3 and 10.3 years of age. Abnormal SEPs indicated subclinical cervical
myelopathy in 3 subjects. Cervical cord compression may be present before occurrence
of clinical or electrophysiological evidence of myelopathy. However, we feel that
the SEP analysis is useful to detect functional impairment of the cervical cord in
patients with MPS.
Key words
Somatosensory evoked potentials - Subcortical potentials - Mucopolysaccharidosis -
Myelopathy - Child
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Dr. Rainer Boor
Pediatric Neurology University Children's Hospital Johannes-Gutenberg University
55101 Mainz
Germany
Email: E-mail: boor@kinder.klinik.uni-mainz.de