Lumbar Puncture and Brain Herniation in Acute Bacterial Meningitis: A Review

Abstract

There has been controversy regarding the risk of cerebral herniation caused by a lumbar puncture (LP) in acute bacterial meningitis (ABM). This review discusses in detail the issues involved in this controversy. Cerebral herniation occurs in about 5% of patients with ABM, accounting for about 30% of the mortality. In many reports, LP is temporally strongly associated with this event of herniation and is most likely causative based on pathophysiologic arguments. Although a computed tomography (CT) scan of the head is useful to find contraindications to an LP, a normal CT scan in ABM does not mean that an LP is safe. Clinical signs of "impending" herniation are the best predictors of when to delay an LP because of the risk of precipitating herniation, even with a normal CT scan. Some of these clinical signs to be considered are deteriorating level of consciousness (particularly to a Glasgow Coma Scale of <or= 11), brainstem signs (including pupillary changes, posturing, or irregular respirations), and a very recent seizure. The risk of not doing an LP when it is contraindicated because of concern of the risk of herniation is extremely small. In those considered high risk for herniation, interventions to control intracranial pressure, such as attention to airway, breathing, and circulation, with a mannitol infusion and antibiotics started, should be the priorities, followed by an urgent CT scan and not an LP.

Clinical Reasoning: A 44-year-old woman with headache followed by sudden neurologic decline

“…Antibiotics should be administered prior to lumbar puncture (LP), since CSF cultures do not become sterile until 2 hours from antibiotic administration for meningococcus and 6 hours for pneumococcus, and cellular/biochemical changes last 48-68 hours. 1 Dexamethasone is recommended in the treatment of adults with meningitis, based on the results of a randomized trial studying 301 patients. 2 Patients who received dexamethasone (10 mg every 6 hours for 4 days) beginning 15-20 minutes prior to or with the first dose of antibiotics had a significant decrease in unfavorable outcomes and death.…”

“…1 Severe inflammation can cause cerebral edema and impairment of CSF flow. The resultant elevated ICP may create a pressure gradient between the skull contents and spinal column.…”

“…LP may precipitate herniation due to exacerbation of this pressure gradient, though a cause-effect relationship is debated. 1,4 In a review of 98 reported cases of herniation in acute bacterial meningitis, 11% of herniation events occurred prior to LP, 38% occurred within 3 hours of LP, and 41% occurred between 4 and 12 hours following LP. 1 While imaging findings of midline shift and effacement of the fourth ventricle or cisterns are obvious contraindications to LP, CT is insensitive for predicting elevated ICP in the setting of meningitis, since decreased compliance of inflamed meninges and ventricular walls may counteract the forces of cerebral edema, yielding a falsely reassuring ventricular appearance.…”

“…1,4 In a review of 98 reported cases of herniation in acute bacterial meningitis, 11% of herniation events occurred prior to LP, 38% occurred within 3 hours of LP, and 41% occurred between 4 and 12 hours following LP. 1 While imaging findings of midline shift and effacement of the fourth ventricle or cisterns are obvious contraindications to LP, CT is insensitive for predicting elevated ICP in the setting of meningitis, since decreased compliance of inflamed meninges and ventricular walls may counteract the forces of cerebral edema, yielding a falsely reassuring ventricular appearance. 1,5 Seizures, focal neurologic deficits, papilledema, and altered consciousness may predict increased ICP in the setting of normal-appearing radiologic images in acute meningitis.…”

“…1 While imaging findings of midline shift and effacement of the fourth ventricle or cisterns are obvious contraindications to LP, CT is insensitive for predicting elevated ICP in the setting of meningitis, since decreased compliance of inflamed meninges and ventricular walls may counteract the forces of cerebral edema, yielding a falsely reassuring ventricular appearance. 1,5 Seizures, focal neurologic deficits, papilledema, and altered consciousness may predict increased ICP in the setting of normal-appearing radiologic images in acute meningitis. 1,6 While some experts propose that these clinical signs warrant performance of CT prior to LP, 7 others suggest that their presence should lead to deferment of LP.…”