Extradural spinal cyst

Posted by Dr.Chakravarthi Dr.Chakravarthi
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28 year male a readymade shop owner, father of two healthy babies, not a smoker or alcoholic came with complaint of progressive weakness of both the legs over last 4 months which was preceded by back pain.

The pain was precipitated by movements- first time he noticed when he was getting up from the bed in the morning. Pain was aggravated by lifting wait, walking and relieved by lying down. No special posture to relieve the pain. Not radiating to the legs.

Pain remained there for around a week to 10 days after which it subsided. Progressively, he developed heaviness of the legs with mild dull aching pain localized in both the knee joints.

Over last three months he is finding it difficult to walk and since a month, he can walk only with support. There is history of inappropriate erection at the time of ejaculation over the last 4 months. There is no bladder/ bowel/ sensory disturbance. .
There is no relevant personal or family history.

Clinical examination:

On examination his higher CNS functions were normal. Gait could not be tested.
He had 2/5 to 4/5 hypertonic paraparesis, more proximally with brisk KJs and AJs and bilateral upgoing plantars. His joint and vibration sensations were impaired in both legs. Other sensations were normal.
There was tenderness over the thoracic spines with no kypho-scoliosis, no tuft of hair, lipoma, hyperpigmented patch or wasting of muscles.


Radiology:

Surgery, (D4 to D9 laminectomy) revealed a shiny grey colored avascular wall cystic lesion with a connecting stalk to the intradural space. It was excised in to after tying a knot around the stalk.




A short note on Extradural meningeal cysts:

1 to 3% of total spinal tumors. They are congenital in origin, as a result of  out pouching of the arachnoid layer.
It has been reported in all age groups with a slight preponderance in females.
Clinically it presents with symptoms of cord and the root compression- as the location and extent may be. Back ache, leg weakness the commonest presentation.
Urinary incontinence, impotence, numbness of legs might be others.
On examination corroborative findings will be obtained.

Commonest sites are Thoracic, thoraco- lumbar, sacral, and cervical, in that order.

Histopathological confirmation of the nature of the cell wall (arachnoid) is not always possible; hence they are named as meningeal cyst. Foci of calcification may be seen. The cyst contains clear fluid like CSF.  

They are graded by NABORS et al
Type- I- extradural arachnoid cyst without nerve roots
Type-II- extradural arachnoid cyst with nerve roots
Type-III- Intradural arachnoid cyst.
Type IB- Sacral meningocele (occult sacral meningocele

X- Rays  do not show any thing specific other than signs of probable space occupying lesion.
Earlier myelogram was the confirmatory test to show the contrast agent leaking in to the extradural space.
With advent of MRI some people advocate total replacement of myelography – but some times,  myelogram may help find the site of arachnoid connection. CT myelography is a usefull technique for the same Reasons.

Differential diagnosis includes epidermoid/ dermoid, enterogenous cyst, teratogenous cys.

Surgical excision is the choice. Closure of the dural defect/ connecting stalk with the arachnoid space is vital or else CSF leak will occur. Prognosis is good with total excision and tying the stalk. Intra dural lesions may recur.