[Evoked potentials in Chiari-malformation type I with syringomyelia--a case history].

The Chiari-syndrome Type I being a malformation of the posterior cranial fossa often leads to syringomyelia. The disease becomes apparent in adolescence with kyphoscoliosis, headache, vertigo, ataxy, hearing loss, partial paralysis and other neurological disorders. The onset is typically characterized by dissociated anesthesia, due to the frequent localization of the syrinx in the neighborhood of the posterior column of the spinal cord. It is reported a case of an 15-years-old-girl suffering from intensive headache, recurrent left-sided paresthesias and progredient scoliosis. Somatosensory evoked potentials of left ulnar and tibial nerves revealed a complete loss of cortical response. Diagnostic imaging showed an Chiari-malformation I with herniation of cerebellar tonsils and secondary syringomyelia of the cervical spinal cord. After surgical treatment with posterior fossa decompression, C1 laminectomy and partial excision of cerebellar tonsils the patient had a clear improvement in symptoms. Postsurgical the width of cervical syrinx decreases. Now somatosensory evoked potentials of the left ulnar and tibial nerves show amplitude-reduced cortical responses with a normal latency.