Intra-dialytic intracranial pressure monitoring in a patient with idiopathic intracranial hypertension and dialysis disequilibrium syndrome

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INTRODUCTION: Dialysis disequilibrium syndrome (DDS) is a rare neurological manifestation of intermittent HD, thought to be due to promotion of cerebral oedema and characterised by symptoms of raised intracranial pressure (ICP). DDS does not respond to either steroids or Mannitol.

We present a 25year old female with focal segmental glomerulosclerosis (FSGS) in established renal failure (ERF) with a lumbo-peritoneal (LP) shunt for idiopathic intracranial hypertension (IIH). She commenced HD aged 18years. Following investigations for loss of vision, diagnosis of IIH was made and LP shunt was placed age 20years in order to preserve eyesight. She continued to have headache during HD; opening pressure upon lumbar puncture was 16cmCSF. The headache was attributed to low CSF pressure, exacerbated by fluid shifts during HD. As she was due to be transplanted 3 months later, she did not wish for shunt revision. Cessation of HD led to relief of headache.

METHODS: Her initial valve-less LP shunt system was revised upon sustaining low pressure headache to a shunt with a 5:35cm gravitational valve. Unfortunately she developed recurrent FSGS in her transplant after 2 years and recommenced HD. Her HD-associated headache returned and she became distressed by this. ICP monitoring was undertaken while on the HD unit, to determine if the headache was due to intracranial pressure change.

Due to the gravitational valve in her LP shunt, CSF drainage via the shunt occurs at a higher opening pressure when upright. She was advised to dialyse in a recumbent position. This reduced shunt valve opening pressure. This increased CSF drainage, reducing ICP during HD and relieving headache.

RESULTS: We expected to discover low pressure headache during HD, due to a functioning LP shunt. Conversely, ICP tracing during HD revealed a progressive rise in ICP, from a baseline below 5mmHg, culminating at over 20mmHg, with spikes above 40mmHg. This rise correlated with reported symptoms of headache during HD. Thus, DDS was confirmed as the cause of headache.

CONCLUSION: We believe these results support the theory of raised ICP during HD in patients with DDS. Cerebral oedema is a likely causative factor for raised ICP but is not definitively proven by ICP measurement alone. It is however feasible that an osmotic shift of water occurring as a result of rapid clearance of small molecules during HD could cause cerebral oedema and raised ICP. In IIH, where the patient is already at risk of raised ICP and has reduced cerebral compliance, relatively small pressure changes caused by cerebral oedema may be enough to make the patient symptomatic.

Our results confirm evidence of raised ICP during HD in support of DDS, in a patient with previously diagnosed IIH. A gravitational valve in her LP shunt gave us a unique opportunity to lower her intracranial pressure during HD with positional change alone. This greatly improved her symptoms. ICP monitoring in a dialysis patient is rare; we recommend it is considered for those with a neurosurgical history who sustain unexplained and disabling headache.

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