Diastematomyelia (Split Cord Malformation)
Diastematomyelia (split cord malformation) is a rare congenital anomaly in which the spinal cord is split in the sagittal plane. A bony or fibrous septum may lie between the two half-cords (hemicords). Tethered cord and vertebral anomalies frequently accompany it, and surgery is required in cases with progressive symptoms.
最后更新: 2026-06-07
Definition
Diastematomyelia (Greek for 'split spinal cord') is a form of spinal dysraphism in which the spinal cord is divided in the sagittal plane into two half-cords (hemicords). It arises from errors during early embryonic development of the notochord (the precursor of the spine) and the neural tube; the split usually spans several vertebral levels in the lumbar or thoracic region.
Types (Pang Classification)
According to the Pang classification there are two main types. In type I each hemicord lies within a separate dural sheath, with a bony or fibrocartilaginous septum between them; this is surgically more complex. In type II both hemicords lie within a single dural sheath, with no septum or only a thin fibrous band; in these cases release of the tethered cord is usually sufficient. This distinction is important because it directly affects surgical planning.
Associated Conditions
Diastematomyelia is usually not isolated. Vertebral anomalies (hemivertebra, block vertebra, spina bifida occulta, a widened interpedicular distance) accompany the majority of cases. Almost all cases have some degree of tethered cord. Congenital scoliosis is common and may be progressive. Other dysraphic anomalies such as lipoma, dermal sinus and syringomyelia may also be present.
Symptoms
Symptoms are variable. Skin findings over the back, such as a hair tuft, hemangioma, dermal sinus or dimple, point to an underlying anomaly. Progressive symptoms from tethered cord usually begin in childhood: typically asymmetric leg weakness, gait disturbance, foot deformities (pes cavus), a leg-length discrepancy, bladder-bowel dysfunction and back and leg pain. Congenital scoliosis may become apparent in early childhood and worsen during periods of rapid growth.
Diagnosis
Spinal magnetic resonance imaging (MRI) is the reference method, showing the split cord, the presence and nature of any septum, the state of the dural sheath (separate in type I, single in type II), tethered cord and associated anomalies. On plain radiographs, a widened interpedicular distance is a characteristic clue. Computed tomography (CT) gives a detailed assessment of a bony septum and vertebral anomalies and aids surgical planning. Urodynamic studies are performed in patients with bladder symptoms.
Treatment
Treatment involves resection of the septum and release of the tethered cord (detethering) in type I, and usually release alone in type II. Intraoperative neurophysiological monitoring helps protect the spinal cord. Surgery is recommended in cases with progressive neurological symptoms and in type I cases with a prominent bony septum; the goal is to halt progression and preserve existing function. In cases where spinal fusion is planned for congenital scoliosis, diastematomyelia surgery is usually performed before the scoliosis surgery. In asymptomatic type II cases, observation may be preferred.
Course
With early diagnosis and appropriate surgery, it is usually possible to halt progressive symptoms; pain and bladder symptoms often improve, while established motor deficits may recover only partially. In some cases re-tethering can develop after surgery and require revision. Accompanying congenital scoliosis requires separate follow-up and often surgery. Outcomes vary with the timing of diagnosis, the type and associated anomalies, and none can be guaranteed.
参考文献
- Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th ed. Thieme; 2023:292-293.
- Pang D, Dias MS, Ahab-Barmada M. Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations. Neurosurgery. 1992;31(3):451-480.
- Mahapatra AK, Gupta DK. Split cord malformations: a clinical study of 254 patients and a proposal for a new clinical-imaging classification. J Neurosurg. 2005;103(6 Suppl):531-536.
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