To the Editor:—
The case report by Ganapathy et al. 1of alleged transient neurologic symptoms following intrathecal ropivicaine and their subsequent anatomy-based defense 2of deJong's 3criticism forgets a very important principle: anatomic variation.
Ganapathy et al. 2state:“The spinal cord ends at the level of L1, and our spinal puncture was performed at L2–L3.” Maybe yes, maybe no. Hogan, 4in an elegantly simple letter to the editor, cogently cites earlier anatomic studies 5 6pointing to the clinical importance of understanding that what lies beneath the lumbar vertebral bodies (via counting palpable bony landmarks relative to Tuffier's Line) may be unreliable and that the conus medullaris may be as low as L3. Nothing in the report by Ganapathy et al. 1accurately (i.e. , radiographically) documents the level of their dural puncture (their experience notwithstanding) and is a major reason why accuracy of ascertaining proper vertebral levels based on surface anatomy may be only 50%. 7In other words, we probably are not where we think we are more than we realize. Perception of paresthesia may be blunted in the sedated patient and preclude patient report. Similarly, more information to the obliquely mentioned first attempt at dural puncture needs to be provided to assuage the suspicion correctly raised by deJong 3before accepting their contention of a chemical etiology for the symptoms observed.
Blind faith in normative anatomic relationships as evidenced by Ganapathy et al. 2does not refute deJong's 3excellent criticism of their case report. The time course and constellation of problems Ganapathy et al. 1describe does not resemble transient neurologic symptoms as presently recognized. 8Their case report, by the details not mentioned concerning the circumstances, site(s), and degree of patient sedation during multiple attempts at dural puncture lends credence to the suspicion that their patient experienced mechanical trauma to underlying neural structures due to anatomic misadventure while performing dural puncture.
Regular and occasional practitioners of subarachnoid anesthesia would be well served by attempting dural puncture in as caudad an interspace as possible, reserving higher lumbar approaches as backup choices for technically difficult patients while recognizing the inherently increased risk attendant at those levels.