![]() ![]() Although fluoroscopic guidance certainly facilitates access to the spinal canal in patients with obesity, the greater variability in the LP technique may affect OP accuracy. The transition from LD positioning, historically favored among neurologists, to an increasing number of LPs performed in the prone position is the consequence of more LPs being performed by radiologists. In the discussion of proper LP technique, Friedman et al ( 6) clarify that the LD position is the most accurate means of measuring OP and that sedation and Valsalva should be avoided. These OP threshold criteria were based on the aforementioned studies of normative data derived from LPs performed in the LD position. The most updated criteria for the diagnosis of definite pseudotumor cerebri syndrome (PTCS) require a “properly performed” LP with OP greater than 25 and 28 cm H 2O in adults and children, respectively ( 6). Avery et al ( 3) found the 90% CI to be 11.5–28 cm H 2O in children. Whiteley et al ( 5) found the 95% confidence intervals (CIs) for OP measured in the LD position among 242 adults to be 10–25 cm H 2O. In adults, these studies collectively show a median OP of 17–19 cm H 2O ( 4,5). The bulk of OP normative data is based on LPs performed in the LD position ( 3–5). Since the conception of the LP, neurologists have favored the LD position because it facilitates both anatomical access to the spinal canal and reduces the risk of falsely elevated OP inherent with other positions. Failure of the Queckenstedt maneuver to induce ICP elevation in the appropriate time frame was considered an indication of spinal canal obstruction. He reported a test, later termed the Queckenstedt maneuver, in which manual jugular vein compression and Valsalva maneuver were performed to increase central venous pressure (CVP), followed 10–12 seconds later by increased intracranial pressure (ICP) as measured by lumbar manometer. By 1916, Hans Heinrich Georg Quenckenstedt, a German neurologist with an interest in CSF dynamics, described performing LPs in the LD position using a manometer to measure OP ( 2). The notion of accessing the cerebrospinal fluid (CSF) via the lumbar spinal canal dates back to 1891 when a German surgeon, Heinrich Quincke, first described the procedure as a therapy for hydrocephalus ( 1). Theory, eminence, and evidence support the century-old medical mantra that the lateral decubitus (LD) position during LP is the most accurate means of measuring OP and that prone positioning often leads to spuriously elevated OP measurements. Pro: Prone Positioning During Lumbar Puncture Affects Opening Pressure Measurement in a Clinically Meaningful Way: Collin McClelland, MD Two experts debate whether positioning during LP is clinically significant. Diagnostic lumbar puncture (LP) is increasingly being performed by neuroradiologists, with variability in positioning during the measurement of opening pressure (OP). ![]()
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