Nerve root anomalies: implications for transforaminal lumbar interbody fusion surgery and a review of the Neidre and Macnab classification system

Abstract

<jats:p>Lumbar nerve root anomalies are uncommon phenomena that must be recognized to avoid neural injury during surgery. The authors describe 2 cases of nerve root anomalies encountered during mini-open transforaminal lumbar interbody fusion (TLIF) surgery. One anomaly was a confluent variant not previously classified; the authors suggest that this variant be reflected in an amendment to the Neidre and Macnab classification system. They also propose strategies for identifying these anomalies and avoiding injury to anomalous nerve roots during TLIF surgery. Case 1 involved a 68-year-old woman with a 2-year history of neurogenic claudication. An MR image demonstrated L4–5 stenosis and spondylolisthesis and an L-4 nerve root that appeared unusually low in the neural foramen. During a mini-open TLIF procedure, a nerve root anomaly was seen. Six months after surgery this patient was free of neurogenic claudication. Case 2 involved a 60-year-old woman with a 1-year history of left L-4 radicular pain. Both MR and CT images demonstrated severe left L-4 foraminal stenosis and focal scoliosis. Before surgery, a nerve root anomaly was not detected, but during a unilateral mini-open TLIF procedure, a confluent nerve root was identified. Two years after surgery, this patient was free of radicular pain.</jats:p>

Current occurence of intraspinal intradural and extradural communicating branches in the spinal canal

“…Symptoms of radiculopathy may manifest intraspinal variations of nerve roots even in cases of the absence of pressure on nerve roots (5,6,9,22). Some papers are based on surgical fi ndings (23); others are based on anatomical studies (9,12).…”

“…Some papers are based on surgical fi ndings (23); others are based on anatomical studies (9,12). Their incidence ranges from 1.3% found during the operation (6) to 2-6.7 % detected by imaging methods before surgery (9,11,16,22), and from 8.5 % to 30 % during the study of cadavers (6,22).…”

Accessory Nerve Root and associated dural injury incidences encountered during lumbar microdiscectomy performed for lumbar disc hernias

“…During this kind of surgery, nerve root abnormalities may be encountered 15 . Some authors separated accessory nerve root abnormalities into three, fi ve or six groups 5,6 . Th e most commonly used is the Neidre and MacNab classifi cation.…”

“…According to the Neidre and MacNab classifi cation, nerve root abnormalities were divided into six groups 6 . Berta et al detected conjoined nerve root abnormalities in four out of 80 patients 16 .…”

“…Awareness of an accessory nerve root abnormality reduces intraoperative injuries 6 . During surgery, certain complications may develop such as dural tear, nerve root injury and vascular injuries which are mostly due to anatomical variations or intraoperative diffi culties of the exploration of the surgical fi eld 1,7 .…”