Diastematomyelia

 

Vigy Elizebth Cherian

Assistant Professor, Sharda University, Greater Noida, NCR, Delhi

 

ABSTRACT:

Split spinal cord malformation (SSCM) is a rare form of spinal dysraphism in which a person is born with splitting, or duplication, of the spinal cord. It may be characterized by complete or incomplete division of the spinal cord, resulting in two 'hemicords.' There are two types of SSCM. In type I, each hemicord has a full protective covering (thecal sac) and they are separated by a bony structure, forming a double spinal canal. In type II, the two hemicords are surrounded by one thecal sac and there is a single spinal canal. Some people may not have symptoms, while others may have a tethered cord and/or various other spinal abnormalities. Treatment may include surgery for release of a tethered cord, and/or physical therapy for neurologic problems or pain.

 

 

INTRODUCTION:

Diastematomyelia is a rare congenital anomaly that forms from an abnormal adhesion between ectoderm and endoderm results in the "splitting" of the spinal cord in a longitudinal (sagittal) direction. This abnormal adhesion which splits the cord may be in the form of fibrous tissue or purely a calcific bar or purely an ossific bar or even a combination of the earlier mentioned entities. It is more common in females (3:1)¹. This condition occurs in the presence of an osseous (bone), cartilaginous or fibrous septum in the central portion of the spinal canal which then produces a complete or incomplete sagittal division of the spinal cord into two hemicords. When the split does not reunite distally to the spur, the condition is referred to as a diplomyelia, or true duplication of the spinal cord².

 

DEFINITION:

Diastematomyelia (occasionally diastomyelia) is a congenital disorder in which a part of the spinal cord is split, usually at the level of the upper lumbar vertebra, It is also known as a split cord malformation².

 

INCIDENCES:

Split cord malformations are a congenital abnormality and account for ~5% of all congenital spinal defects. It is more common in the lower cord but can sometimes occur at multiple levels¹.

·       50% occur between L1 and L3

·       25% occur between T7 and T12

 

An associated bony, cartilaginous or fibrous spur projecting through the dura mater forwards from the neural arch is visible in 33% of cases¹

 

CAUSES:

Abnormal stretching of the spinal cord².

 

CLASSIFICATION:

Split cord malformations are divided into two types according to the presence of a dividing septum and single vs dual dural sac:

·       Type I: Duplicated dural sac, with common midline spur (osseous or fibrous) and usually symptomatic

·       Type II: Single dural sac containing both hemicords; impairment less marked

 

 

 

Type I:

Type I is the classic diastematomyelia, characterized by

·       Duplicated dural sac

·       Hydromyelia common

·       Midline spur often present (osseous or osteocartilaginous)

·       Vertebral abnormalities: hemivertebrae, butterfly vertebrae, spina bifida, fusion of laminae of adjacent levels

·       Skin pigmentation, hemangioma and hypertrichosis (hair patch) are common

·       Patients are usually symptomatic presenting with scoliosis and tethered cord syndrome³

 

Type II:

Type II is milder than type I, and lacks many of the features of latter:

·       Single dural sac and no spur/septum

·       Cord divided, sometimes incompletely

·       Hydromyelia may be present

·       Spina bifida may be present, but other vertebral anomalies are far less common

·       Patients a less symptomatic or may even be asymptomatic³

 

CLINICAL FEATURES:

The majority of patients with diastematomyelia are symptomatic, presenting with signs and symptoms of tethered cord, the onset of symptoms is anytime from birth to adult life. Among newborns, the presence of an abnormal tuft of hair over the spine or an associated meningoceles often brings the defect to attention

 

Although patients with mild type II may be minimally affected or entirely asymptomatic. Presenting symptoms include:

·       Leg weakness

·       Low back pain

·       Scoliosis

·       Incontinence

 

Patients with diastematomyelia also frequently have other associated anomalies including:

·       Meningocele

·       Neurenteric cyst

·       Dermoid cyst

·       Clubfoot

·       Spinal cord lipoma

·       Hemangioma overlying spine⁴

 

DIAGNOSTIC FINDINGS:

·       Antenatal ultrasound

The presence of an extra echogenic focus in the midline between the fetal spinal posterior elements has been described as a reliable sign.

 

·       Plain radiograph

·       Multilevel spina bifida

·       Widening of interpedicular distance: but this may be remote from the site of the spur

·       associated scoliosis

·       Anteroposterior vertebral body narrowing⁵

·       CT

 

It is able to better image many of the features seen on plain films and in addition may demonstrate the bony septum⁵.

 

·       MRI

It is the modality of choice for assessing children with split cord malformations. MRI provides definitive visualization of the defect. Its being able to elegantly demonstrate the cord and presence of hydromyelia (if present), it can also access for the presence of the numerous associated anomalies⁵

 

 

MANAGEMENT:

The surgical procedure required for the effective treatment of diastematomyelia includes decompression (surgery) of neural elements and removal of bony spur. This may be accomplished with or without resection and repair of the duplicated dural sacs. Resection and repair of the duplicated dural sacs is preferred since the dural abnormality may partly contribute to the "tethering" process responsible for the symptoms of this condition. Surgical removal of the septum and general freeing of the cord from any tethering action helps prevent the further development of cord dysfunction⁴.

 

REFERENCES:

1.      Peter S. Harper. Central nervous system disorders. Practical Genetic Counselling. London: Arnold; 2003; 176

2.      Ersahin Y, Kitis O, Oner K. Split cord malformation in two sisters. Pediatr Neurosurg. November, 2002; 37(5):240-244

3.      Prasad VS, Sengar RL, Sahu BP, Immaneni D. Diastematomyelia in adults. Modern imaging and operative treatment. Clin Imaging. 1995; 19: 270–274

4.      Anderson NG, Jordan S, Macfarlane MR et-al. Diastematomyelia: diagnosis by prenatal sonography. AJR Am J Roentgenol. 1994;163 (4): 911-4

5.      Williams RA, Barth RA. In utero sonographic recognition of diastematomyelia. AJR Am J Roentgenol. 1985;144 (1): 87-8

 

 

 

Received on 30.10.2019          Modified on 16.11.2019

Accepted on 30.11.2019     © A&V Publications all right reserved