Dr. Sher Mohammad and authors discuss Tethered Spinal Cord Syndrome, its causes and pathophysiology
TSCS refers to a group of neurological disorders that relate to malformation of the spinal cord [1]. This is a group of dysraphic conditions in which the conus medullaris is located in an abnormally low position and is fixed there in a relatively immobile state. The disorders include tight filum terminals, lipomeningocele, split spinal cord malformations, dermal sinus tracts and dermoids. Previously, this disorder was termed the filum terminale syndrome.
The term TSCS was coined in 1976 by the Canadian neurosurgeon Harold J Hoffman [2] and colleagues, who described a series of patients with neurologic symptoms associated with low conus and/or thick filum identified on iophenyldate myelography. Since then, the concept of TSCS has expanded beyond the tight filum and now many of the dystrophic conditions that were excluded by Hoffman and colleagues are considered typical aetiologies under the umbrella of TSCS.
Normal Spinal Cord
The cord consists of a long bundle of axons and interneurons that connect the sensory and motor neurones within the spinal cord. The spinal cord is connected to the base of the brain and is continuous to the filum terminale at the bottom.
The filum terminale which is composed of glial tissue (supportive structure of nerve cells) and covered by pia mater, is a delicate strand of fibrous tissue, bridging the spinal cord tip and the sacrum. Due to its high viscoelasticity, the filum terminale allows movement of the spinal cord. If abnormal fibrous tissue grows into the filum and replaces glial tissue, the filum loses its elasticity and abnormally fixes (tethers) the spinal cord, and becomes a mechanical cause of tethered cord syndrome. The inelastic filum is commonly thickened in children, but found less frequently in adults.
Sagittal Section of Lumbo-sacral vertebral Canal
- Spinal Cord ends
- Dura mater
- Subarachnoid Space
- Filum Terminale ends at first coccygeal segment
Pathophysiology of TSCS
Normally the spinal cord ascends in the vertebral canal as the spinal column starts to grow faster than the spinal cord at 9th week of gestation. Consequently, the spinal cord is pulled upwards due to the growth difference. Barson’s studies showed that in the 20-week embryo, the conus medullaris terminated at the L4-5 level [3]. By the term, conus had ascended to L3 and by two month of postnatnatal age, the conus reached the adult L1-2 level. Tethering of the conus prevents this normal ascent. Yamada’s st