Review Question - QID 214717

This patient’s headache is likely caused by idiopathic intracranial hypertension due to the elevated opening pressure in a patient with obesity. This patient’s normal CT head, white-to-red blood cell ratio in the range of 1:750-1000 in the cerebrospinal fluid (CSF), and absence of xanthochromia are consistent with a traumatic lumbar puncture (LP).

Traumatic LPs occur when the needle passes through the subarachnoid space and there is accidental trauma to the capillaries or venules. Trauma to these structures introduces red and white blood cells into the CSF. LPs are often performed in the emergency department when there is high suspicion for a subarachnoid hemorrhage even though a CT head without contrast does not demonstrate blood. There are a number of factors to take into consideration when differentiating a traumatic LP from a subarachnoid hemorrhage. A declining red blood cell count in successive CSF collection tubes is suggestive of a traumatic LP; however this decline can also occur in subarachnoid hemorrhage. The absence of xanthochromia is more consistent with a traumatic LP than a subarachnoid hemorrhage, especially when performed with spectrophotometry. The presence of xanthochromia suggests that blood has been present in the CSF for at least 2 hours. Traumatic LP introduces 1 WBC for every 750-1,000 RBCs. CSF protein and glucose are typically elevated in traumatic LP.

Silverstein et al. studies the seasonality of neuroophthalmic manifestations of pediatric lyme disease. The authors found that most of the 212 cases at a tertiary care center presented during the summer. 50 patients presented with neuroborreliosis, 24 had meningitis, and 6 had optic disc edema. The authors recommend that opening pressures should be obtained if lyme meningitis is suspected.

Incorrect Answers:
Answer 1: Bacterial meningitis typically presents with sudden onset fever, nuchal rigidity, severe headache, and altered mental status. Patients may also have positive Kernig and Brudzinski signs, suggesting meningeal inflammation. CSF profile usually demonstrates glucose < 40 mg/dL and white blood cell count > 1,000/uL.

Answer 2: Herpes encephalitis typically presents with altered mental status and focal neurological deficits, such as cranial nerve palsies, hemiparesis, and focal seizures. CSF profile usually demonstrates elevated white and red blood cell count and protein.

Answer 3: Lyme meningitis typically presents with fever, headache, nuchal rigidity, and photosensitivity. Patients also develop cranial neuropathies, such as Bell palsy. CSF white blood cell count and protein are typically elevated.

Answer 4: Subarachnoid hemorrhage presents with acute onset headache that reaches maximum severity over a short period of time (“thunderclap headache”). Xanthochromia of the CSF is present in nearly all patients with subarachnoid hemorrhage; its absence effectively excludes this diagnosis.

Bullet Summary:
Traumatic lumbar puncture is suggested by the absence of xanthochromia, declining red blood cell count in successive cerebrospinal fluid collection tubes, and a cerebrospinal fluid white-to-red blood cell ratio of 1:750-1,000.