Common Indications for Lumbar Puncture
The most common diagnostic indication for LP is suspicion of CNS infections. Apart from that, CSF is essential for the diagnosis of various neuro-inflammatory conditions viz Primary CNS Vasculitis,3 autoimmune encephalitis,4 acute transverse myelitis,5 and Guillain-Barre Syndrome.6 CSF study provides circumstantial evidence in the diagnosis of Multiple Sclerosis and helps distinguish it from other inflammatory demyelinating diseases like NMO-MOG.7 CSF can be used to confirm the diagnosis of subarachnoid haemorrhage, when the results of brain imaging are inconclusive, by analysing degraded haemoglobin particles in CSF.8 CSF cytology can identify suspected leptomeningeal metastases, and CSF flowcytometry can corroborate in the diagnosis of CNS.9 CSF opening pressure of >25cm H2O is essential for the diagnosis of Idiopathic Intracranial Hypertension.10 A normal opening pressure and improvement in gait after removal of 30-50 ml CSF confirms the diagnosis of Normal Pressure Hydrocephalus and predicts the efficacy of CSF catheter placement.11
A lumbar puncture can be used therapeutically—e.g. intrathecal colistin, vancomycin in ventriculitis,12 intrathecal interferon in SSPE,13 intrathecal nusinersen in SMA,14 intrathecal chemotherapy,15and intrathecal baclofen for spasticity.16Perioperative intrathecal fluorescein injection helps visualization of CSF leaks at the skull base.17 Headache caused by raised intracranial pressure in acute communicating hydrocephalus and cryptococcal meningitis can be relieved by draining CSF by LP18 and is associated with a 69% relative improvement in survival.19 In patients with IIH, with imminent visual loss, a lumbar puncture can be used as a rescue measure to save vision before other definitive CSF diversion procedures can be planned.20