Introduction: Paroxysmal unilateral cephalic hyperhidrosis is a rare disorder of the autonomic nervous system. Case report: We report an adult male who developed this disorder almost 20 years after posterior fossa decompression for Chiari I malformation with syringomyelia as a child. Further, the patient presented with spastic diplegia. To date, this patient has refused further operative intervention. The medical literature is reviewed regarding this unusual phenomenon. Conclusion: To our knowledge, hyperhidrosis of the occiput has not been previously reported in a patient with Chiari I malformation with an associated syringomyelia. © Springer-Verlag 2006.