Spinal cord atrophy associated with split cord malformation (Diastematomyelia)

A 60-year-old male presented to the outpatient department with complaint of lower back pain persisting for the last 5 years. Additionally, he reported progressive weakness in both upper and lower limbs over the last 6 months. There is no history of trauma, and the patient denies experiencing bowel or bladder incontinence.

The MRI results showed several significant findings:

• Split cord malformation (Diastematomyelia): Split cord detected below the D11–D12 level within a single dural sac, indicating type 2 diastematomyelia (Figures 1a and 1b).
• Subdural arachnoid cysts: A large CSF-filled cyst in the lower cervical region causing compression on the spinal cord, resulting in atrophy. Communication with surrounding CSF was not evident without myelography (Figures 2a, 2b and 2c).
• Hydromyelia: Observed at the C7–D2 level (Figure 3c).
• Intradural neurenteric cyst: A small cyst found on the ventral surface of the spinal cord at the D4 level (Figures 3a and 3b).
• Tethered cord: Conus located at L4 level, suggesting tethering (Figure 4). In addition to the above mentioned findings, other associated imaging findings include spinal canal expansion in the antero-posterior dimension, bifid spinous processes, and block vertebrae.

In summary, these findings point to complex spinal anomalies across multiple levels of the cervical and dorsolumbar spine, which could be contributing to the patient’s symptoms of lower back pain and progressive limb weakness.

Split cord malformation (SCM) is a rare spinal cord abnormality where the spinal cord is divided into two parts, either symmetrically or asymmetrically [1]. This division can be due to an osseous or fibrocartilaginous septum within the spinal cord, leading to a complete or incomplete separation [2]. Each part, called a hemicord, has its own central canal, anterior horn, posterior horn, and is surrounded by its own layer of pia mater [1,3].

Split cord malformation (SCM) most commonly occurs in the dorsolumbar spine, primarily affecting the lower thoracic and upper lumbar vertebrae. The cervical region is less commonly affected by SCM [4]. Its origin is thought to be related to abnormal progression of notochord development between the 15th and 18th day of pregnancy [3,5]. This anomaly is believed to arise from a fundamental developmental error around the time of closure of the primitive neurenteric canal.

Pang’s 1992 classification simplifies split cord malformations (SCMs) into two types:

• Type I: Characterised by a bony or fibrous spur with separate dural sacs and arachnoid spaces around each hemicord. This type is often symptomatic due to compression or tethering of neural elements by the spur.
• Type II: Typically asymptomatic or rarely symptomatic, lacking a bony spur. There is no clear separation of dural sacs or arachnoid spaces, and the division of the spinal cord is usually more subtle compared to type I SCM [1].

Split cord malformation (SCM) can occur alone, usually with a better prognosis [3]. However, it can also be associated with other spinal dysraphisms such as meningocele, lipomeningocele, myelomeningocele, neuroenteric cysts, spinal arachnoid cysts and spinal lipoma with tethered cord. Additionally, SCM may be accompanied by vertebral anomalies like scoliosis, haemangioma, hemivertebrae, and butterfly vertebrae [1,3,7]. These associated conditions can complicate the clinical presentation and management of SCM. MRI is the gold standard for diagnosis, providing detailed images for accurate assessment [8].

Management of diastematomyelia often starts with conservative measures, such as pain management, physical therapy, and close monitoring for symptom progression or complications. Surgical intervention may be warranted if there is substantial neurological compromise, spinal instability, or other significant issues.

Conclusions

Split cord malformations (SCMs) are rare spinal anomalies where the spinal cord divides into two parts. They can occur alone or with other spinal abnormalities, leading to symptoms like back pain, neurological deficits, and bowel/bladder dysfunction. Subdural arachnoid cysts, if untreated, can worsen and contribute to weakness below the compression site. MRI is the diagnostic tool of choice. Management varies from conservative measures to surgery, depending on the case.