# A Rare Case of Non-traumatic Tension Pneumocephalus Following a Lumbar Puncture: Unusual Complications of a Common Procedure

## TL;DR

A 66-year-old woman developed a rare brain complication after a routine spinal tap, likely due to an undetected skull defect.

## Contribution

This is one of the first reported cases of tension pneumocephalus following a lumbar puncture in a healthy individual with a hidden skull base defect.

## Key findings

- Tension pneumocephalus occurred after a lumbar puncture in a patient with a previously undiagnosed lateral sphenoid encephalocele.
- A negative intracranial pressure gradient from the lumbar puncture likely caused a CSF leak and air ingress through the skull base defect.
- The encephalocele acted as a one-way valve, worsening the pneumocephalus and highlighting the risk of routine procedures in such cases.

## Abstract

Tension pneumocephalus is a rare but severe complication characterized by intracranial air accumulation, leading to increased intracranial pressure (ICP). While it is most commonly associated with trauma, surgical interventions, tumors, or infections, spontaneous cases related to skull base defects and cerebrospinal fluid (CSF) leaks are uncommon. We present what we believe to be one of the first reported cases of tension pneumocephalus following a diagnostic lumbar puncture (LP) in an otherwise healthy individual with no predisposing history, prior history of skull base trauma or surgery. The patient was a 66-year-old female who presented with altered mental status. Initial non-contrast CT brain scans showed no evidence of pneumocephalus, though incidental left sphenoid sinus opacification was noted. Following the LP, the patient’s neurological symptoms worsened, and subsequent imaging revealed tension pneumocephalus. Further evaluation confirmed a focal dehiscence in the posterolateral wall of the left sphenoid sinus, with herniation of brain tissue consistent with a lateral sphenoid encephalocele. We hypothesize that the LP induced a negative ICP gradient, precipitating a CSF leak and ingress of air through the skull base defect. As intracranial air pressure increased, the encephalocele likely functioned as a one-way "ball-valve" mechanism, exacerbating the tension pneumocephalus. This case highlights the potential for routine diagnostic procedures to result in serious complications in patients with undiagnosed skull base defects. Detecting subtle encephaloceles and areas of skull base dehiscence can be difficult on non-contrast imaging, emphasizing the need for high clinical suspicion, especially when evaluating for CSF leaks. Multidisciplinary management and early recognition of such anatomical vulnerabilities are critical in preventing life-threatening complications associated with tension pneumocephalus.