Cranio-cervical decompression for Chiari I malformation. A retrospective evaluation of functional outcome with particular attention to the motor deficits.

We report a series of 26 patients affected by a Chiari I malformation treated at our department between 1987 and 1993. All patients underwent pre- and postoperative evaluation by magnetic resonance imaging (MRI). Sequential perioperative motor evoked potential (MEP) recordings were performed in 8 patients. The preoperative symptoms can be divided into four subgroups: cephalgias (84.6%), cranial nerve deficits (69.2%), motor deficits (76.9%), sensory deficits (73%). Twenty-five out of 26 patients underwent craniovertebral decompression, 1 a transoral anterior decompression. One patient died 2 months after surgery because of progressive pulmonary failure. We registered following postoperative complications transient hypoglossal palsy (1 case), vertigo (2 cases), meningitis (1 case), minor CSF leaks (3 cases). Cephalgias subsided in 17 and improved in 4 out of 22 patients. Cranial nerve deficits improved in 8 and were stabilized in 7 out of 18 patients. A limited recovery of trigeminal function was possibly due to nuclear lesions. Five patients whose vestibular disturbances were not relieved by surgery were put on a course of carbazepine. Vertigo resolved in one case and in two others improved. While hypesthesia improved after decompression, the other sensory deficits were stabilized in 5% of the patients. Spasticity improved in 12 out of 18 patients, but weakness only in 7 out of 17 patients. Motor disturbances were always detected by MEP-recording. MEP-characteristics were not specific, resembling those of patients with other intra-, extramedullary myelopathies. Functional recovery was not matched by an improvement of the MEP parameters. MEP may be used as tool for surveillance of patients whose clinical findings are not progressive and are not at first surgical candidates.