Interesting Read!..

Cauda Equina and Conus Medullaris Syndromes

Author: Segun T Dawodu, MD, JD, MBA, FAAPMR, FAANEM, CIME, DipMI(RCSed),

Introduction

Background

The spinal cord tapers and ends at the level between the first and second lumbar vertebrae in an average adult. The most distal bulbous part of the spinal cord is called the conus medullaris, and its tapering end continues as the filum terminale. The upper border of the conus medullaris is often not well defined. Distal to this end of the spinal cord is a collection of nerve roots, which are horsetail-like in appearance and hence called the cauda equina (Latin for horse's tail). These nerve roots constitute the anatomic connection between the central nervous system (CNS) and the peripheral nervous system (PNS). They are arranged anatomically according to the spinal segments from which they originated and are within the cerebrospinal fluid (CSF) in the subarachnoid space with the dural sac ending at the level of second sacral vertebra.

Transient Loss of TcMEP during L5-S1 posterior fusion?

In the following case report, a posterior lower lumbar surgical procedure done on a Spondylolisthesis (L5/S1) patient resulted in a transient loss of motor evoked potentials despite the patient had no neurological injury?. The motor loss was occurred after epidural injection of 2.4mg of morphine?. The authors believe it could be due to the pressure caused by the injection would have compressed cauda equina?.

Even a small injection of this kind could lead to evoked potential changes should be noted. Though the TcMEP recovered after 1h, care  must be taken to make sure prolonged compression does not take place!.

Case report

Transient loss of motor-evoked responses associated with caudal injection of morphine in a patient with spondylolisthesis undergoing spinal fusion

PETER R.J. GIBSON MBBS FANZCA*, Pediatric Anesthesia, Volume 16 Issue 5, Pages 568 - 572, 2005

A 7-year-old girl having posterior spinal fusion for Grade 3 anterior spondylolisthesis at the L5/S1 level was administered 2.5 mg of morphine in 10 ml saline via the caudal epidural route before surgery.

Motor-evoked responses were markedly diminished in her lower limbs for 1 h following this but returned spontaneously. She suffered no neurological injury. The cause for this is postulated to be transient cauda equina compression from the volume of injectate. This complication of caudal injection has not been reported before. The possible mechanisms for this are discussed. We believe that significant L5/S1 spondylolisthesis should be considered a contraindication to the use of caudal epidural injections.