Low-pressure headaches result from reduction in cerebrospinal fluid (CSF) volume and pressure due to lumbar puncture or spontaneous or traumatic CSF leaks.
(See also Approach to the Patient With Headache.)
Removal of CSF by lumbar puncture (LP) reduces CSF volume and pressure, as do spontaneous or traumatic CSF leaks.
Headache after LP is common, usually occurring hours to a day or two afterward, and can be severe. Younger patients with a small body mass are at greatest risk. Using small, noncutting needles reduces risk. The amount of CSF removed and duration of recumbency after LP do not affect incidence.
Spontaneous CSF leaks may result when a nerve root arachnoid diverticulum or cyst along the spinal canal ruptures. Coughing or sneezing may cause the rupture. CSF may leak after certain head or facial injuries (eg, basilar skull fractures).
Headache results when head elevation while sitting or standing stretches the pain-sensitive basal meninges. Headaches are intense, postural, and often accompanied by neck pain, meningismus, and vomiting. Headache is alleviated only by lying completely flat.
Diagnosis of Post-LP and Other Low-Pressure Headaches
Clinical evaluation
Post-LP headache is clinically obvious, and testing is rarely needed; other low-pressure headaches, regardless of cause, may require brain imaging. MRI with gadolinium often shows evidence of low CSF pressure, with diffuse enhancement of the pachymeninges and, in severe cases, downward sagging of the brain.
CSF pressure is typically low or unobtainable if patients have been upright for any length of time.
Spontaneous CSF leaks are more difficult to diagnose and should be considered in patients with orthostatic headache relieved by recumbency.
Treatment of Post-LP and Other Low-Pressure Headaches
Usually an epidural blood patch
The first line of treatment for post-LP headache is
Recumbency
Hydration
An elastic abdominal binder
Analgesics as needed
However, if post-LP headache persists after a day of such treatment, an epidural blood patch (injection of a few mL of the patient’s clotted venous blood into the lumbar epidural space) is usually effective. A blood patch may also be effective for spontaneous or traumatic CSF leaks, which rarely require surgical closure. The blood patch is thought to increase the pressure in the epidural space, decreasing the rate of the CSF leakage, regardless of where the CSF leak is. If normal CSF production exceeds the rate of leakage, the symptoms resolve.
