Goal of the Study?
In this review article from the open access World Journal of Orthopedics 1 the authors’ goal was to provide a comprehensive review and analysis of the clinical features, radiological imaging aspects and the neurophysiological characteristics of Far Lateral Lumbar Disc Herniation.
Why are they doing this study?
Neural foramina are critical structures in the spine that contain exiting nerve roots. Approximately 10% of systematic lumbar disc herniations are located within or lateral to the neural foramen. Intraforaminal and extraforaminal lumbar disc herniations, usually referred to as Far Lateral Lumbar Disc Herniations (FLLDH) can compress the spinal nerve and dorsal root ganglion leading to severe, sometimes excruciating pain. FLLDH does not respond well to conservative management and usually requires surgery. FLLDH is a distinct category of lumbar disc herniation, which is characterized by unique clinical manifestations and requires a greater diagnostic and therapeutic effort than the more common median and paramedic localizations of disc hernia. The diagnosis of FLLDH is more demanding and still underestimated as it requires detailed knowledge in spine anatomy and dedicated radiological studies.
What was done?
A series of FLLDH articles were reviewed to determine the epidemiology, clinical presentation, diagnostic imaging and neurophysiology currently used to detect FLLDH.
What did they find?
Far lateral disc herniations differ from their more common postero-lateral counterparts in the following ways:
- they involve the nerve root exiting at the same level;
- they may have a positive femoral stretch test;
- pain and paresthesia can be reproduced by lateral bending to the side of disc herniation and;
- pain is often more severe than central disc herniation
If an appropriate procedure is followed MRI is the best imaging modality for diagnosing FLLDH. If an MRI scan is not possible a multi-slice CT scan is a good second option. The distinction between intraforaminal and extraforaminal herniations must be correctly diagnosed before the right surgical procedure can be chosen. Neurophysiology is a complementary yet crucial tool in the diagnosis of FLLDH as it aids in the differential diagnosis of radiculopathy and other disorders, as well as verification of the implicated level. It may also reveal the extent of the damage to the brain.
Why do these findings matter?
The correct surgical strategy of FLLDH depends on a preoperative diagnosis and thorough location of the extracanalicular herniated disc. Root compression lies beyond the lateral extension of the subarachnoid space, thus cannot be seen on the myelographic images. At the present time, only MRI and computed tomography can show the disc herniations in the level of detail necessary for surgery. One reported study found that there was a 30% chance of misdiagnosis on the initial CT or MRI report.
At Dynamic Disc Designs, we create far lateral disc herniation models that dynamically extrude the nucleus pulposus. Being specific regarding disc herniation location can be very important when exploring therapeutic strategies.