Lumbar punctures: use and diagnostic efficiency in emergency medical departments

Background: Lumbar punctures (LP) are regularly and effortlessly used in the emergency medical departments (EMD). LP use and efficiency have not been fully explored in the published literature.

Aims: The goal of this study was to assess in a French EMD, the frequency of use and the diagnostic efficiency of LP, the final diagnoses, and related medical practices.

Methods: We retrospectively studied all patients who underwent an LP after admission to our adult EMD in 2004 and 2005. Patients' medical files were reviewed to collect clinical and paraclinical features. We defined efficient LP as abnormal LP, which confirmed a suspected diagnosis in an emergency setting.

Results: A total of 247 patients, representing 0.5% of all admissions, underwent an LP. LP were efficient in fewer than 15% of cases and confirmed aseptic meningitis (8.5%), bacterial meningitis (2.4%), Guillain-Barré syndromes (1.6%), subarachnoid hemorrhages (SAH, 0.4%), and carcinomatous meningitis (0.4%). The principal differential diagnoses were infections outside the central nervous system (CNS, 30%), noninfectious neurological disorders (28.7%), and benign headaches (14.2%). The main assumed LP indications were to search for CNS infection (62%) and for SAH (25%). LP efficiency decreased dramatically according to patients' age. Brain imaging was performed in 90% of patients prior to LP. Excessive use of polymerase chain reaction to detect herpes simplex in cerebrospinal fluid was observed. The only LP complications found were postdural puncture headaches (6.1% of cases). The rate of traumatic LP was 17%.

Conclusions: Our results are in accordance with the few published surveys on this topic. LP efficiency is modest but must be considered in light of the seriousness of suspected diagnoses. However, the search for differential diagnoses should not be neglected.