Spontaneous regression of a chiari malformation type 1 in a 58-year-old female.

Studies have established a complex age-related variation of the position of the cerebellar tonsils relative to the foramen magnum (FM). Chiari malformation type 1 (CM1) is generally defined by a protrusion >5 mm from the FM and may be an asymptomatic incidental finding. Symptoms include headache, nausea and neurological disturbances, including trigeminal neuralgia. Moreover, tonsils are often peg shaped and associated with syringohydromyelia. Symptomatic CM1 may be managed with decompression of the posterior cranial fossa, but spontaneous regression in adults has been reported occasionally. Theories include restoration of normal cerebrospinal fluid dynamics around the FM after rupture of subarachnoid adhesions or the syrinx itself during transient episodes of raised intracranial pressure. Supratentorial neurosurgery has also been implicated. We present a 58-year-old female diagnosed with CM1 and no associated syringohydromyelia following MRI investigation of trigeminal neuralgia. Managed medically, she re-presented 6 years later with new neurological symptoms. A subsequent MR study of the posterior cranial fossa showed resolution of the CM1, with only residual tonsillar ectopia. At no point was intracranial intervention performed, nor were there any events that might favour CM1 regression. This case demonstrates spontaneous resolution of CM1 without surgical intervention.