title: Treatment of secondary tonsillar herniation by lumboperitoneal shunt revision.
abstract: BACKGROUND
  Idiopathic intracranial hypertension (IIH) is a condition that usually affects young, obese women. Management is aimed at controlling symptoms of increased intracranial pressure (ICP) and prevention of visual failure due to papilledema. A common surgical treatment for IIH is the insertion of a lumboperitoneal shunt (LP shunt). Secondary symptomatic tonsillar herniation is an uncommon side effect following lumbar cerebrospinal fluid diversion.
  
  
  METHODS
  We present two cases of symptomatic secondary tonsillar herniation, one associated with a syrinx, in patients with IIH following valved LP shunting. Treatment options for this side effect may include transplanting the shunt to the ventricular system or decompression of the foramen magnum.
  
  
  RESULTS
  In our cases we elected to alter the construct of the LP shunt by inserting a programmable valve which led to clinical and radiological reversal of the tonsillar herniation as well as a dramatic reduction in an associated syrinx.
  
  
  CONCLUSIONS
  When faced with LP shunt induced symptomatic secondary tonsillar herniation, consideration may be given to altering LP shunt dynamics, prior to inserting a ventricular catheter into normal sized ventricles or decompressing the posterior fossa.
authors.affiliation: Division of Neurosurgery, University of Alberta, Edmonton, AB, Canada.
authors.forename: Fred C
authors.initials: FC
authors.lastname: Lam
authors.forename: Matthew B
authors.initials: MB
authors.lastname: Wheatley
authors.forename: Vivek
authors.initials: V
authors.lastname: Mehta
mesh_terms: D000328:Adult; D002526:Cerebellar Diseases / Q000209:etiology / Q000601:surgery*; D002557:Cerebrospinal Fluid Shunts / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D019299:Decompression, Surgical / Q000379:methods*; D004677:Encephalocele / Q000209:etiology / Q000601:surgery*; D005260:Female; D006547:Hernia / Q000209:etiology; D059685:Herniorrhaphy; D006801:Humans; D019586:Intracranial Hypertension / Q000150:complications* / Q000601:surgery; D008159:Lumbar Vertebrae; D010529:Peritoneal Cavity; D011559:Pseudotumor Cerebri / Q000150:complications / Q000601:surgery; D016896:Treatment Outcome