Clinical study
Predicting the outcome of shunt surgery in normal pressure hydrocephalus

https://doi.org/10.1016/j.jocn.2006.03.028Get rights and content

Abstract

We studied retrospectively the effectiveness of the repeated lumbar CSF tap test (RTT), lumbar external CSF drainage (LED) and radioisotope cisternography (RIC) in predicting the outcome of shunt surgery, as well as the diagnostic and prognostic value of periventricular hyperintensity (PVH) and of the classic clinical triad in normal pressure hydrocephalus.

Two hundred and seventy patients were referred to the Departments of Neurosurgery, in Nancy, France and in Istanbul, Turkey. The decision to perform surgery was based on the clinical presentation (all patients had at least two symptoms of the classic clinical triad), neuroimaging examinations and the results of the RTT (taps were performed on three consecutive days and at each tap a minimum of 30 to 40 cc of CSF was removed), the LED (drainage was performed for 3 days and the volume of CSF drained daily was a minimum of 150 to 250 cc) or the RIC. After all shunt procedures, postoperative assessments verified improvements in 88% of the RTT group, 91% of the LED group and 66% of the RIC group. Gait disturbance had improved in 90% at the end of the second and twelfth month follow-up. Cognitive dysfunction had improved in 79% at the second and in 77% at the twelfth month follow-up. Urinary incontinence had improved in 66% at the second and in 62% at the twelfth month follow-up. From the surgical point of view, the greatest difficulty is not to make the diagnosis, but rather to identify the appropriate patients to operate on. The decision to perform shunt surgery should be based on strict clinical findings associated with CT and MRI criteria and especially with positive RTT or LED test results.

Introduction

Normal pressure hydrocephalus (NPH) was first described by Adams and Hakim1 as a clinical syndrome with the classic symptom triad of dementia, gait disturbance, and urinary incontinence combined with widening of the cerebral ventricles, but without overt symptoms or signs of raised intracranial pressure. The symptoms are potentially reversible, and diversion of cerebrospinal fluid (CSF) either by a ventriculoperitoneal, ventriculoatrial or lumboperitoneal shunt can be successful, provided a correct diagnosis has been made.

Patient selection for cerebrospinal fluid diversion in NPH is difficult and remains a diagnostic and therapeutic challenge: many patients do not display the classic clinical and neuroimaging patterns, NPH mimics other neurodegenerative disorders such as Binswanger disease (subcortical white matter arteriosclerotic encephalopathy) or Alzheimer’s disease and many patients with suspected NPH may suffer from both disorders and shunt procedures do not always result in clinical improvement. Hence, the usefulness of a shunt may be questioned. Even though the surgical procedure is technically simple, there are risks of complications, both short- and long-term, hence various methods and clinical tests have been used to predict the outcome of a shunt procedure.

In the study of any dementia or gait impairment syndrome, NPH is of particular interest as it may be treated and cured. However, prediction of which patients will benefit from surgery is one of the most important aspects of diagnosis.2 Our departments have used three methods for several years to select patients assumed to have NPH for shunt surgery: the repeated lumbar CSF tap test (RTT), lumbar external CSF drainage (LED) and radioisotope cisternography (RIC), explained in detail later.

We studied retrospectively the effectiveness of RTT, LED and RIC in predicting the outcome of shunt operations, as well as the diagnostic and prognostic value of periventricular hyperintensity (PVH) and of the clinical triad in 270 unselected patients with suspected NPH.

Section snippets

Material and methods

The study covers the period between December 1983 to December 2003, when 291 patients with suspected NPH were referred to the Departments of Neurosurgery at the University Hospital in Nancy, France and Haydarpasa Numune Education and Research Hospital in Istanbul, Turkey. The patients and close relatives were informed and gave their consent for all aspects of the treatment. They all fulfilled the clinical criteria of presumed NPH, but 21 had to be excluded for the following reasons: refusal to

Repeated lumbar CSF tap test

This test was performed on 155 patients and resulted in clinical improvements in 129, who were consequently shunted. Following surgery 111 of these were considered as having improved when evaluated according to the criteria mentioned previously. During follow-up 10 shunts needed revision because of temporary clinical deterioration; two ventricular and eight peritoneal catheters were revised. For 18 patients who did not improve after surgery, revision of their shunt was proposed, 10 accepted,

Discussion

Normal pressure hydrocephalus is in many ways a misnomer. Cerebrospinal fluid (CSF) pressure is not normal in these patients.[4], [11] The historical labelling NPH was based on the finding that all three reported patients by Adams and Hakim1 showed low CSF pressures at lumbar puncture, namely 150, 180, and 160 mm H2O. It is now widely recognized that a single, limited-in-time, CSF pressure measurement by lumbar puncture yields a poor estimation of the real intracranial pressure (ICP) profile of

Conclusion

The results suggest that both the RTT and the LED can accurately predict the outcome of shunt surgery prior to shunt procedures in patients with suspected NPH. The low costs and the simplicity of these tests compared to the invasiveness and the possibility of serious test-related complications of other tests show their usefulness in managing patients with presumed NPH. It has been shown that good results after shunting can be expected in patients showing improvement after a CSF tap test, so

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