Chapter 114. Lumbar Puncture

A 54-year-old morbidly obese man described the “worst headache” of his life and mild photophobia to an examining physician. His medical history did not reveal any risk factors for increased intracranial pressure (age > 60 years, immune-compromised state, presence of CNS disease, new onset of seizure, confusion, or symptoms suggestive of focal neurologic abnormalities). His physical examination was notable for a temperature of 100.5°F, alert and appropriate mental status, supple neck examination, and the absence of focal neurologic findings (hemiparesis, aphasia, visual field cuts, or cranial nerve palsies). His physician ordered immediate empiric antibiotics prior to a head CT scan. A proceduralist performed an ocular ultrasound which demonstrated an optic nerve sheath diameter (ONSD) of 5.8 mm in the left eye and 6.0 mm in the right eye. Because the ONSD was elevated, a CT scan of his brain without contrast was obtained and reported no acute bleed, midline shift, or mass effect.

Using ultrasound guidance and a 22 g × 124 mm Gertie Marx needle, a lumbar puncture was performed to rule out subarachnoid hemorrhage and meningitis. Because of his girth, the patient sat upright during the procedure. After return of fluid was noted, the proceduralist replaced the stylet and gently lowered the patient to the left lateral position. The proceduralist documented an opening pressure of 380 mm Hg with the patient relaxed and breathing comfortably and the presence of respiratory variation in the manometer. He removed 40 cc of colorless CSF for diagnostic evaluation and recorded a closing pressure of 170 mm Hg. The WBC count was 300 with predominant neutrophils and the RBC count was zero. The results of the spinal tap (300 WBCs/hpf with predominant neutrophils and zero RBCs/hpf) were consistent with the diagnosis of acute meningitis and the patient was admitted for continued intravenous antibiotic therapy.