Lumbar puncture for idiopathic intracranial hypertension diagnosis [Neurosurgery Wiki]

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====== Lumbar puncture for idiopathic intracranial hypertension diagnosis ======

{{rss>https://pubmed.ncbi.nlm.nih.gov/rss/search/1DAyVQqGr_VI4_2VT0Y8vRXS_i6lKV9V4e8Cem6Qi8G6wWusuA/?limit=15&utm_campaign=pubmed-2&fc=20240909112817}}

Lumbar puncture is performed to measure the opening pressure, as well as to obtain cerebrospinal fluid (CSF) to exclude alternative diagnoses. If the opening pressure is increased, CSF may be removed for transient relief.

Lumbar puncture is performed routinely for diagnostic and therapeutic purposes in idiopathic intracranial hypertension, despite lumbar puncture being classically contraindicated in the setting of raised intracranial pressure.
((Paruchuri S. R. A., Lawlor M., Kleinhomer K., Mason L., Johnson C. Risk of cerebellar tonsillar herniation after diagnostic lumbar puncture in pseudotumor cerebri. Anesthesia and Analgesia. 1993;77(2):403–404. doi: 10.1213/00000539-199308000-00039.)).

It has been postulated that the reason herniation does not occur in this setting is a reduction in [[brain compliance]] due to persistently high [[ICP]] 
((Salman M. Why does tonsillar herniation not occur in idiopathic intracranial hypertension? Medical Hypotheses. 1999;53(4):270–271. doi: 10.1054/mehy.1998.0756.))

A 30-year-old female with known idiopathic intracranial hypertension who had cerebellar tonsillar herniation following therapeutic lumbar puncture. Management followed guidelines regarding treatment of traumatic intracranial hypertension, including rescue decompressive craniectomy. Hoffman et al. hypothesize that the changes in brain compliance that are thought to occur in the setting of idiopathic intracranial hypertension are protective against further neuronal injury due to axonal stretch following decompressive craniectomy.
((Hoffman KR, Chan SW, Hughes AR, Halcrow SJ. Management of Cerebellar Tonsillar
Herniation following Lumbar Puncture in Idiopathic Intracranial Hypertension.
Case Rep Crit Care. 2015;2015:895035. doi: 10.1155/2015/895035. Epub 2015 Jan 18.
PubMed PMID: 25685562; PubMed Central PMCID: PMC4313522.))

A 30-year-old woman with coexisting renal tubular acidosis and idiopathic intracranial hypertension (IIH), treated with acetazolamide, experienced coning (cerebellar tonsillar herniation) after a lumbar puncture (LP). Brain magnetic resonance imaging at initial diagnosis of IIH showed minor tonsillar descent and computed tomographic venography revealed hypoplasia of the left transverse sinus. The patient previously had three uneventful LPs, all of which showed high opening pressures and normal cerebrospinal fluid composition. In retrospect, it was noted that her serum bicarbonate had fallen to 9 mmol/L (normal: 22-28 mm/L) 1 week before the LP. We hypothesize that the combination of cerebral edema (due to worsening metabolic acidosis), poor venous drainage, and preexisting minor tonsillar descent contributed to her post-LP coning
((Borire AA, Hughes AR, Lueck CJ. Tonsillar Herniation After Lumbar Puncture in 
Idiopathic Intracranial Hypertension. J Neuroophthalmol. 2015 Mar 16. [Epub ahead
of print] PubMed PMID: 25786203.
)).

====Laboratory findings====
The CSF is examined for abnormal cells, infections, antibody levels, the glucose level, and protein levels. In IIH, by definition all of these are within their normal limits.

The most frequent abnormal laboratory findings were elevated C reactive protein (CRP) (51 %), thrombophilia (31 %), increased plasma cortisol levels (29 %) and elevated lactate dehydrogenase (LDH) (20 %). Patients with elevated CRP and patients with thrombophilia had an unfavorable visual outcome. Increased cortisol levels and abnormal calcium correlated with a higher rate of recurrence. The visual outcome of patients with elevated LDH was better than those with normal LDH. It seems that certain metabolic, inflammatory and coagulation abnormalities may influence the course of IIH. If confirmed in further studies, these findings could contribute to elucidation of the etiology and prognosis of IIH.
((Pollak L, Zohar E, Glovinsky Y, Huna-Baron R. The laboratory profile in idiopathic intracranial hypertension. Neurol Sci. 2015 Jul;36(7):1189-95. doi:10.1007/s10072-015-2071-y. Epub 2015 Jan 18. PubMed PMID: 25596710.)).