Neurological Disorders: Syringomyelia

Introduction

Syringomyelia means a cavity or cyst (syrinx) within the spinal cord (myelia) most often filled with some fluid.

Syringomyelia is a neurological disorder and a similar condition that involves the brain stem area is called as syringobulbia (bulb in this context means lower brain stem or medulla oblongata where syrinx of brain usually occurs).

Types & Causes

A congenital type of syrinx is seen when somebody born with it. Certain types of chiari malformation are associated with syrinx in the spinal cord.

Acquired types are due to or related with the following conditions of the spinal cord;

• Traumas/injuries
• Tumors
• Spinal meningitis
• Arachnoiditis
• Stroke (bleeding or infarct) etc.

What causes a syrinx?

Although the exact mechanisms that creates cavity or cystic area in the spinal cord or brainstem is not clear however it may be due to destruction and death of nerve fibers in a focal area of these structures and subsequent cavity formation.

The above hypotheses holds good for syrinx formation due to acquired causes as above and for cerain congenital forms too. However there are other postulated mechanisms also, for example an abnormal pattern of CSF flow may result in the formation of a cystic area in the spinal cord called as hydromyelia (also as syrinx by some authorities).

Clinical Presentation

A syrinx in the spinal cord may present with certain distinct neurological syndromes depending upon its location, or simply present with some non specific presentation.

The distinct syndromes associated with a syrinx usually are;

• Brown Sequard syndrome
• Hanging sensory loss
• Dissociative sensory loss
• Central cord syndrome etc

Please see that none of the above syndromes are specific for syrinx, also not all syrinx will present with these syndromes.

Brown Sequard syndrome (hemi spinal cord syndrome) pattern is seen when the syrinx involves only or mainly one half of the spinal cord.

Hanging sensory loss occurs with a syrinx in the cervical spine area or upper spinal cord where the damage to spinal cord causes sensory manifestations in a segmental distribution corresponding to that area, and this looks like hanging because the sensation corresponding to the lower spinal cord is largely normal.

Dissociation sensory loss occurs because syrinx usually grows from inside to outside. More inner or central areas of the spinal cord convey the pain & temperature sensation and the more outer area convey touch, vibration, pressure, joint position sensation etc. Since the central areas are more involved or first involved you see the pain & temperature sensation is lost while the other sensations are relatively spared. So there is dissociation between the loss of sensation.

Central cord syndrome is again related with the discussion in the above paragraph. As the syrinx grows in the central areas first the pain & temperature are preferentially affected especially in the beginning along with some of the motor fibers so certain distinct motor weakness involving the upper and lower limbs may be seen.

Other than the above manifestation patients can simply present with myelopathy, paralysis of jus one limb, hemiparasis, and there can be bowel and/or bladder involvement too.

Generally syrinx manifestations are slowly progressive.

If syringobubia is present then cranial neuropathies, upper and lower limb motor and/or sensory manifestations may be seen in different combinations.

Diagnosis

MRI of the spine with & without contrast is the most relevant investigation. If syringobulbia is suspected then MRI of the brain is ordered too.

CT of spine CT myelogram etc are inferior alternatives to MRI when it comes to syrinx diagnosis because syrinx occur in the spinal cord tissue and MRI shows a picture of it but not the other tests mentioned above.

Treatment

A small syinx, or non symptomatic ones may be left like that. However if the size and symptoms are progressive or symptoms are severe then surgical interventions like draining the syrinx is done. A catheter is placed between the syrinx cavity and the peritoneal cavity.

Syringomyelia patient’s pain, numbness etc are treated generally with medications like gabapentin, pregabalin, duloxetine etc. If muscle weakness is present then physical therapy and occupational therapies may be needed.

Neurologist and Neurosurgeon are frequently involved in the care of patients with Syringomyelia and Syringobulbia.



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