Tethered Cord Syndrome

A unilateral or progressive cavovarus foot, especially with a lumbosacral cutaneous marker like a sacral dimple, must make me consider an underlying tethered cord syndrome - abnormal caudal fixation of the spinal cord, typically a low-lying conus medullaris below L2 with a thickened, often fatty filum terminale, which puts the distal cord under traction and produces progressive neuro-orthopaedic symptoms. The orthopaedic clues are exactly these: a cavovarus foot, asymmetric calf atrophy or a leg-length difference, and scoliosis, particularly atypical or neurological curves; and the cutaneous stigmata - a dimple, hairy patch, subcutaneous lipoma, haemangioma or dermal sinus - are external markers of dysraphism. I would take a careful neurological history and examination of the lower limbs, ask specifically about bladder and bowel function, and arrange an MRI of the spine, which is the key investigation and shows the low conus, the thickened filum, and any associated lesion such as a lipomyelomeningocoele, dermal sinus or split-cord malformation; in an infant, spinal ultrasound can screen before the posterior elements ossify. I would also obtain a urological assessment, including urodynamics, because neurogenic bladder is common and is an important reason to act.

Once the diagnosis is confirmed on MRI and the patient assessed across the neurological, urological and orthopaedic domains, the treatment is surgical untethering - releasing the tethering element, most simply by sectioning a tight or thickened filum terminale, or addressing a more complex dysraphic lesion. The principle is that untethering relieves the traction on the cord to halt progression and, where possible, allow some improvement, and the procedure can be done through a limited, even minimally invasive, exposure with hemilaminectomy, durotomy and filum separation. I would manage the patient within a multidisciplinary team of neurosurgery, urology and orthopaedics. In counselling the family, I would explain that the main goal of surgery is to stop further deterioration; symptoms that are recent or progressing may improve after untethering, but established neurological or urological deficits may not fully reverse, which is why timely surgery in a symptomatic or deteriorating patient is important. I would also explain that the foot deformity, scoliosis and bladder will continue to be monitored and managed in their own right, and that there is a possibility of re-tethering over time requiring follow-up.