Tethered Cord Syndrome and the Conus in a Normal Position

In its classic form, TCS implies a low-lying conus medullaris.There is some variation in the definition of an "abnormally" low conus. To some, below the L1-2 disc space is abnormally low, whereas to others, below the inferior aspect of the L-2 vertebral body is abnormally low. Both definitions refer to Barson's  anatomical measurements. Reimann and Anson ^[62] demonstrated in an autopsy study in the normal adult population that the spinal cord terminates at or above the inferior aspect of the L-2 vertebral body in 95% of the population and that it terminates at or above the L1-2 disc space in 57% of the population (Figure 9). The conus medullaris reaches its mature adult level approximately 3 months after full-term gestation.Tethered cord syndrome may occur in the presence of a conus in the normal position. In patients who present with TCS in the setting of a conus in a normal position, the same frequency of the following is seen: cutaneous stigmata of OSD (46% compared with 52%), extremity abnormalities (39% compared with 32%), bone abnormalities (100% compared with 95%), dysraphic anomalies (62% compared with 78%), and neurological abnormalities (77% compared with 87%) as patients with TCS in the setting of a low-lying conus, respectively. None of the patients studied with TCS in the setting of a conus in a normal position presented with urological dysfunction as the only abnormality, and this patient population appeared to be different from that in whom a tight filum terminale is expressed solely in the presence of a hyperreflexic neurogenic bladder and a conus at a normal level.

Tethered Cord Syndrome in Adults

 The late onset of presentation may be related to the cumulative effects of repeated microtrauma during flexion and extension. Some authors have noted distinct precipitating events preceding symptoms in approximately 60% of the adult patients. Such precipitating factors include heavy lifting, traumatic injury, and the lithotomy position. Tethered cord syndrome in the adult population is similar to that in the pediatric population with respect to the incidence of cutaneous stigmata of OSD, neurological abnormalities at presentation, vertebral and orthopedic anomalies, and specific dysraphic elements.In the adult population, however, TCS is accompanied by nondermatomal low-back and leg pain in 50 to 78% of patients.

 

The Normal Conus and the Hyperreflexic Neurogenic Bladder

Urinary incontinence from bladder instability is a common problem for which patients present to a urologist.Urodynamic studies in the setting of incontinence often reveal detrusor hyperreflexia.The occurrence of urinary incontinence has two age-related peaks: it occurs in children less than 10 years of age and in adults between 60 and 80 years of age. There is a wide variety of medical and urological treatments for bladder instability-related urinary incontinence. In the pediatric and young adult populations, there is an annual spontaneous cure rate for urinary incontinence of 14 to 16% in each age group up to 19 years of age.