An important but not widely recognised complication of lumboperitoneal shunting is the development of a Chiari 1 deformity and syringomyelia. We present a case of a patient who developed symptomatic cerebellar tonsillar descent and syrinx formation following treatment of pseudotumour cerebri with lumboperitoneal shunting.

Case report

A 31 year old woman was diagnosed with pseudotumour cerebri following development of headaches, loss of vision, and papilloedema, in association with a cerebrospinal fluid (CSF) opening pressure of 36 cm H₂O. Cranial imaging showed an attenuated ventricular system and no other abnormality. In particular, the posterior fossa was satisfactory in appearance. She was treated with lumboperitoneal shunt insertion, with resolution of her symptoms.

Twelve months later, the patient reported a 6 month history of left hemisensory loss, left arm weakness, and unsteadiness. Neurological examination revealed wasting and reduced power of the intrinsic muscles of the left hand, and left-sided hyperaesthesia to pin-prick. Magnetic resonance (MR) imaging showed the development of cerebellar tonsillar descent and syringomyelia throughout the cervico-thoracic spinal cord. The patient underwent insertion of a low pressure ventriculoperitoneal shunt and removal of the lumboperitoneal shunt, with subsequent symptomatic improvement. There was, however, no resolution of the syrinx on follow up MR imaging.

Discussion

The development of cerebellar tonsillar descent is a recognised but rarely reported complication following lumboperitoneal shunting,^1–5 usually in the treatment of communicating hydrocephalus.^1,3,5 It has been reported to occur in a large proportion of paediatric patients undergoing this procedure, with Chumas et al reporting a 70% incidence in this age group,¹ but its incidence in the adult population is undefined. The development of secondary syringomyelia appears to be much less common, with the above paediatric patients reporting an incidence of syrinx formation of 4%. The development of Chiari 1 and syringomyelia formation following lumboureteral shunting for the treatment of pseudotumour cerebri is recognised but has been less commonly reported.^2,4,5

There is a small number of papers reporting chiari development following lumbar shunting for communicating hydrocephalus in children, but only two case reports of syringomyelia formation.

The association of syrinx formation and cerebellar tonsillar descent through the foramen magnum is well described,⁶ and is postulated to occur as a consequence of a cranial-spinal CSF pressure gradient and diversion of CSF down the central canal of the spinal cord rather than over the cerebral convexities.^3,4,6 It would seem remarkable that this complication is not seen more commonly in the treatment of pseudotumour cerebri.

The non-resolution of the syrinx, in our case following lumboperitoneal shunt removal, is consistent with other workers’ experiences, although resolution has been reported in one instance.⁷

In conclusion, we describe the development of Chiari 1 deformity and syrinx formation as an important but otherwise poorly recognised complication of lumboperitoneal shunting in patients with pseudotumour cerebri.