Is Lumbar Puncture Needed? - Noninvasive Assessment of ICP Facilitates Decision Making in Patients with Suspected Idiopathic Intracranial Hypertension

PURPOSE

 Idiopathic intracranial hypertension (IIH) usually occurs in obese women of childbearing age. Typical symptoms are headache and sight impairment. Lumbar puncture (LP) is routinely used for both diagnosis and therapy (via cerebrospinal fluid drainage) of IIH. In this study, noninvasively assessed intracranial pressure (nICP) was compared to LP pressure (LPP) in order to clarify its feasibility for the diagnosis of IIH.

MATERIALS AND METHODS

 nICP was calculated using continuous signals of arterial blood pressure and cerebral blood flow velocity in the middle cerebral artery, a method which has been introduced recently. In 26 patients (f = 24, m = 2; age: 33 ± 11 years), nICP was assessed one hour prior to LPP. If LPP was > 20 cmH₂O, lumbar drainage was performed, LPP was measured again, and also nICP was reassessed.

RESULTS

 In total, LPP and nICP correlated with R = 0.85 (p < 0.001; N = 38). The mean difference of nICP-LPP was 0.45 ± 4.93 cmH₂O. The capability of nICP to diagnose increased LPP (LPP > 20 cmH₂O) was assessed by ROC analysis. The optimal cutoff for nICP was close to 20 cmH₂O with both a sensitivity and specificity of 0.92. Presuming 20 cmH₂O as a critical threshold for the indication of lumbar drainage, the clinical implications would coincide in both methods in 35 of 38 cases.

CONCLUSION

 The TCD-based nICP assessment seems to be suitable for a pre-diagnosis of increased LPP and might eliminated the need for painful lumbar puncture if low nICP is detected.