Which procedures are performed in the evaluation of hydrocephalus?

Updated: Jun 04, 2018
  • Author: Stephen L Nelson, Jr, MD, PhD, FAACPDM, FAAN, FAAP; Chief Editor: Jasvinder Chawla, MD, MBA  more...
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Lumbar puncture (LP) is a valuable test in evaluating NPH, but should be performed only after CT or MRI of the head. Normal LP opening pressure (OP) should be less than 180 mm H2 O (ie, 18 cm H2 O). Patients with initial OP greater than 100 mm H2 O have a higher rate of response to CSF shunting than those with OPs less than 100 mm H2 O. Improvement of symptoms after a single LP in which 40-50 mL of CSF is withdrawn appears to have some predictive value for success of CSF shunting.

Continuous CSF drainage through external lumbar drainage (ELD) is a highly accurate test for predicting the outcome after ventricular shunting in NPH, although false negative results are not uncommon. [17]

Continuous CSF pressure monitoring can help in predicting a patient's response to CSF shunting in NPH. Some patients with normal OP on LP demonstrate pressure peaks of greater than 270 mm H2 O or recurrent B waves. These patients tend to have higher rates of response to shunting than those who do not have these findings. This procedure also could differentiate NPH from atrophy.

Additionally, ICP monitoring can be helpful in patients with labile intracranial pressure, where an LP may miss the elevation, in determine when shunting may be indicated (for example, pseudotumor patients with persistent headaches despite medical treatment but normalized LP opening pressures).

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