CASE REPORT
A Case of Surgically Treated Adult Split Cord Malformation Type 2 with Tethered Cord Syndrome
2025 Volume 12 Pages 1-5
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2025 Volume 12 Pages 1-5
Split cord malformation (SCM) is a rare congenital anomaly characterised by the division of the spinal cord into 2 distinct hemicords, often accompanied by bony or cartilaginous septum. We experienced a surgical case diagnosed as SCM with tethered cord syndrome (TCS) due to spinal lipoma. A 54-year-old female presented with a history of gradually progressive paraparesis and bladder dysfunction for a few months. Her magnetic resonance imaging revealed low-positioned conus medullaris below the level of S3 due to spinal lipoma and accompanied by other small multiple lipomas and a split cord below the level of L4/L5 without bony separation. The final diagnosis was SCM type II with TCS. Under careful intraoperative inspection, fibrous connecting strings were arising from the dorsal interface of the split cord to the dorsal arachnoid membrane as one of the responsible tethering structures. Circumferential meticulous dissection was performed around the split cord, followed by standard dissection of tethered conus owing to lipoma at the caudal end. Her symptoms were alleviated immediately after surgery. Although the surgical procedure has not been established because of its rarity, dissection around the split cord should precede the usual untethering of the caudal spinal cord.
Split cord malformation (SCM) is a rare congenital anomaly characterised by the division of the spinal cord into 2 distinct hemicords, often accompanied by bony or cartilaginous septum. When SCM coexists with tethered cord syndrome (TCS), neurological deficits and musculoskeletal abnormalities can occur. We present a surgical case of a patient diagnosed with SCM and TCS, emphasising the clinical presentation, diagnostic evaluation, surgical intervention, and postoperative outcomes.
A woman aged 54 years presented with a history of gradually progressive motor weakness and numbness in lower limbs for a few months. The patient also reported difficulty in walking and urinary incontinence. Neurological examination revealed motor weakness (Manual Muscle Testing scale 4/5) without decreased sensation in the bilateral lower extremities. Deep tendon reflexes were within the normal range, and the Babinski sign was negative. The patient underwent surgery of untethering the spinal cord.
Radiographical estimationThe patient's magnetic resonance imaging (MRI) revealed the lower position of conus medullaris below the level of S3 due to spinal lipoma and accompanying the other multiple small lipomas connecting to subcutaneous fatty tissues (Fig. 1). The spinal cord was divided into 2 hemicords below the L4/L5 level, which, on the basis of computed tomography (CT) findings, did not have bony septum between the 2 hemicords within the normal single dura matter, confirming the diagnosis of SCM type 2 with TCS.
Magnetic resonance imaging findings revealed low-positioned conus medullaris (A; arrow) and SCM below L4/L5 level (B; arrowhead) on inverted heavy T2 weighted image, and reunited cord connected to the subcutaneous fatty tissue at the caudal end on T1 weighted image (C; arrow). SCM accompanied with multiple spinal lipomas (D–F; arrowhead). SCM: split cord malformation
The patient underwent untethering of the spinal cord. Intraoperative neurophysiological monitoring was used to ensure the safety procedure; motor evoked potential (MEP) was established at anterior tibialis, plantar, gastrocnemius, and anal sphincter muscle. Skin incision and laminectomy were performed from L5 to the lower sacral level. Intraoperatively, laminectomy of identified spina bifida under microscope and dural incision revealed the split cord without bony septum (Fig. 2). There were fibrous connecting strings arising from the dorsal aspect of the interface of the split cord to the dorsal arachnoid membrane as one of the responsible tethering structures, which was detached. Careful dissection of the thin fibrous septum between 2 hemicords was performed to identify the septum down to the abdominal face below L5 level. The large vein was located inside the septum. No attachment point to the ventral dura could be readily identified. The divided cord united again at S2 level. The lower positioned united cord also adhered to the dura matter both dorsally and abdominally through thick fibrous tissues, which was also one of the causes of the tethered cord. Circumferential dissection of the cord was performed to release the tethered cord; finally, the caudal lipoma was cut after attentive intraoperative nerve stimulation. Two other small lipomas were connected with thin string tissue, each of which resembled a nerve root; however, there was no apparent response to the nerve stimulation, so we dissected both of these lipomas.
Intraoperative findings (rostral side is left) show not bony but fibrous septum between 2 split cords (A), fibrous attachment to the dura (B), and small lipomas (C). Dissection of bottom face at the caudal end of spinal cord (D).
The arachnoid membrane was sutured partially (arachnoid plasty), and expansive dural plasty was performed with multiply harvested fascia. Small quantities of cerebrospinal fluid (CSF) leakage under Valsalva manoeuvre was followed by water-tight fashioned muscle suture. No drainage tube was retained. There was no decrease in the amplitude of MEP during surgery.
Postoperative outcomesThe patient had an uneventful postoperative recovery period. A gradual improvement was noted in lower limb strength during rehabilitation. Postoperative MRI confirmed the successful untethering of the spinal cord (Fig. 3). The patient was discharged home 3 weeks after surgery. During follow-up visits, the patient's urinary incontinence gradually resolved. Serial MRI showed no signs of cord retethering. The patient's permission for this presentation has been obtained.
Postoperative MRI (B) compared with preoperative MRI (A) showed untethered and anteriorly shifted cord. MRI: magnetic resonance imaging
SCM refers to a group of rare spinal dysraphism causing the caudal divergence of a single spinal cord into 2 or more hemicords. SCM is known to be associated with spina bifida, spinal deformity, meningocele, dermal sinus, spinal lipoma, and tethered cord.1,2)
SCM is classified as type I, in which each hemicord has a separate dural sac and is separated by a bony or cartilaginous rigid septum, and type II, in which both hemicords are separated by a nonrigid fibrous tissue within a single dural sac.3) Our case is classified as type II. Various terms have been used for this condition, such as diastematomyelia, dimyelia, dipromyelia, etc., often causing confusion.4,5) Therefore, Pang et al. have advocated use of the expression SCM, taking into account the embryological perspective.1)
Ahmed et al. reported that of the patients with SCM diagnosed above the age of 18 years (N = 146), 25.3% were male, with a mean age of 26.8 years on initial presentation, and SCM type I represented 54.5% of the cohort, with the remaining 45.5% classified as having SCM type II. The most common spinal level was lumbar, with 51.9%, followed by the lumbosacral level (16.9%) and thoracic level (13.2%). Symptoms were neck/back pain in 68.5%, neuropathy/abnormal sensation in 51.8%, leg weakness in 50.9%, and bowel/bladder dysfunction in 27.2% of the patients. MRI indicates separated spinal cord and caudal re-union. In case of SCM type I, CT shows bony septum. The most commonly associated condition was TCS (59.8%), whereas lipoma was only 5.1%.6) Our case was associated with multiple lipomas, which is relatively rare. Xu et al. reported an extremely rare case in which hemicord with SCM type II transited to duplicated filum terminale.7)
Huang et al. mentioned that patients with SCM, including younger patients, represented 78.8% with type I and 21.12% with type II,8) which suggested that type II may be less symptomatic and have a slight delay in onset. Most SCM cases are diagnosed in infancy, and the diagnosis frequently results from myelomeningocele, midline cutaneous abnormalities at the dorsal-lumbar region.9) Nevertheless, SCM with mild skeletal and neurological abnormalities from childhood may be diagnosed in adulthood because of lack of examination. This patient also had hypertrichosis in her back; however, she did not undergo radiographical examination until adulthood. The mechanism of adult onset is secondary degenerative changes with ageing or minor trauma.8) However, adult onset SCM is rare, and the treatment has not yet been established.10)
Surgical intervention is considered in patients with symptomatic SCM. Of the patients with preoperative positive neurological findings, 96.6% showed improvement postoperatively, whereas none of the patients with conservative treatment showed improvement, with 10% having no change and 90% experiencing exacerbation.6) In particular, regarding pain, 91.1% of patients showed improvement; 7.1% remained the same, and 1.8% had exacerbation with surgical intervention, whereas 12.5% showed improvement, 75% had no change, and 12.5% experienced exacerbation with conservative treatment. Patients with progressive neurological deterioration usually show improvement after surgery, especially when the deficits are recent and when pain is a prominent symptom.9) Therapeutic untethering is generally performed in adults on the basis of symptoms. Whether an adult patient without symptoms should undergo prophylactic untethering is not known, given that the natural history is not clear.11) Our patient was also an adult, and her symptoms were gradually exacerbated; she then underwent untethering, which caused alleviation of her symptoms including urinary disturbance.
According to the systematic review,6) laminectomy, untethering, and septum resection was performed in 98.5%, 80.9%, and 70.6% of patients, respectively. Postoperative complications were CSF leak or pseudomeningocele in 2.9%. If the SCM is accompanied by a tethered cord at the sacral level, the septum should be excised first to release the cord. Otherwise, the abruptly released cord will suddenly be pulled upwards (cord retraction against a septum), causing spinal cord injury at the sacral level.6,12) In SCM type I, the spinal cord is anchored by a rigid septum; in contrast, in SCM type II, the presence or absence of the fibrous intradural spur may not be confirmed by either CT scan or MRI. There may be a firm adhesion to both hemicords at the sides and to the dural sac in front and behind; the existence of tethering has been postulated in such patients.1,3) In our case, under careful microscopic inspection, there was fibrous adhesion between the split cord and surrounding dura, which was not detected by thin-slice preoperative MRI. The subsequent release of the caudal tethered cord was intended to avoid spinal cord injury due to traction at the rostral fibrous attachment site, which may produce safer surgery and improvement of neurological deficits. Similar to our case, a case of adult thoraco-lumbar (T12 to L3) SCM type II associated with caudal tethered cord was reported, in which the dissection of adhesion around SCM was performed at L2 level; subsequently, sectioning of the filum terminale was performed through another laminectomy at L5 level.13)
Although adult SCM is quite rare and has no established treatment strategies, patients with progressive neurological deterioration should be considered for timely surgical intervention. In patients with SCM type II, rostral circumferential dissection of fibrous adhesion between the split cord and surrounding dura should precede standard untethering of the caudal end even though the adhesion is not clearly detected by MRI.
The authors have no funding sources to disclose.
Conceptualisation: Miki Fujimura and Motoyuki Iwasaki
Formal Analysis: n/a
Investigation: Motoyuki Iwasaki and Keisuke Ohmae
Methodology: n/a
Project Administration: n/a
Writing-Original Draft: Keisuke Ohmae
Writing-Review and Editing: Miki Fujimura and Motoyuki Iwasaki
Author Miki Fujimura is one of the Editorial Board members of the Journal. This author was not involved in the peer-review or decision-making process for this paper.
All authors have no conflict of interest.
