Plain x-rays of the thoracic spine did not reveal any abnormality. A myelogram via lumbar route showed a complete block of extradural type at T7 vertebral body (Fig. 1). Post-myelo computerised tomography (CT) suggested an extradural mass located posterior to the compressed thecal sac (Fig. 2).

Cavernous angiomas (CA) are uncommon at the spinal level and constitute 5-12% of all spinal vascular anomalies.(17) They may affect any part of the spinal axis and depicts a spectrum of location:

        (1) Vertebral body lesions are clinically rare but found in 12% of the spines at necropsy.(13)
        (2) Vertebral body lesion with epidural extension.(10,13,14, 18,33)
        (3) Pure epidural.(12,19,37,46,47)
        (4) Intradural extramedullary.(33)
        (5) Intramedullary.(39,47)

They are usually solitary but may be associated with CA in other organs or in other parts of the central nervous system.(20,28,44) Sometimes they are familial.(3,6,14)

Epidural CA are rare lesions and comprise less than 4% of all spinal epidural tumours, and 12% of all spinal haemangiomas.(15,43) First description of epidural CA was by Globus and Doshay in 1929 in which they employed the term “epidural haemangioma”.(8) They commonly affect the vertebral bodies and extend intraspinally into the epidural space.(13,46) Purely epidural CA without bony involvement represent a distinct entity and are very rare.(12,13,46) A review of literature revealed at least 75 cases of pure epidural CA.(1,2,5,9,1113,16,19,23,24,28, 29,38,40,45,46) Among these, 24 cases were based on MR studies. Pure epidural CA are most commonly located within the epidural space, less frequently have foraminal extension causing radicular symptoms and there is a single report with intradural extension.(6,12,13,16,23,24,28,32,38,46) They are most frequently located in the thoracic region followed by lumbar region and lastly cervical.(9,10,13,28,30,46) In the thoracic region lesions are usually posterior in location.(9,14,31) In our patient the lesion was located dorsally in the thoracic region extending from T5 to T7.

Cavernous angiomas (cavernomas) are developmental vascular lesions affecting any area and organ system of the body.(13) They may affect central nervous system simultaneously with liver, spleen, kidney, heart and skin.(13,36)

Embryogenesis of CA is debatable. A dysplasia of the angioblastic mesoderm has been considered as a possible origin, whereas others regard these lesions as true haemartomas.(10,13,15,37) It has been postulated that the primitive plexus of vessels may loose the capacity to differentiate with a resultant cavernous malformation, as the primordial vascular plexus with its solitary endothelial lining is indistinguishable from cavernous malformation.(13)

Histologically, these lesions comprise of abnormally dilated irregular sinusoidal vascular channels with thin collagenous wall, either lacking or having very sparse elastic and smooth muscle fibres, lined by solitary flattened endothelium, closely clustered together and not separated by normal neural tissue.(13,17,36) Histologically, immunohistochemically and electron microscopically CA are identical at any location throughout the body.(13) Hemosiderin is almost universally present in intraparenchymal lesions and is sparse or lacking in epidural lesions.(13)

Cavernous angiomas are considered as haemartomas and by definition do not expand by mitototic activity. They may enlarge by internal haemorrhage or by connective tissue proliferation at the outer edge of the lesion.(13,36) Haemorrhage and thrombosis with organisation and recanalisation are the mechanisms of growth with most supportive evidence.(13) Reactive angiogenesis within the bed of haemorrhage is plausible and has been termed “haemorrhagic angiogenic proliferation”.(13) Recruitment with gradual dilation and ectasia of congenitally malformed vessels under hemodynamic stress may be more plausible mechanism causing expansion of epidural and vertebral body lesions.(13) They have a propensity to enlarge and to bleed because of the degree of blood flow and malformed nature of the vessel wall.(12)

The natural history of spinal CA remained less well understood. It appears that these lesions may remain asymptomatic throughout life, while at the other extreme, they may produce disastrous symptoms.(26,42,44) Clinically, four patterns of manifestations can be distinguished:

        (1) slow progressive spinal cord syndrome
        (2) acute spinal cord syndrome
        (3) local back pain
        (4) radiculopathy.(1,6,9,12-14,16,22,24,32,34,36,38)

Most patients presented between 3rd and 5th decades of life with a possible female preponderance.(32,37) Occasional familial occurrence has been reported.(3,20) Some tumours may be associated with cutaneous lesions.(15,18) Small number presenting with acute paraplegia may be related to haemorrhage or infarction within the tumour or sudden increase in size of the lesion following venous thrombosis.(14,18, 21,27,31 )

Plain x-rays may reveal an enlargement of intervertebral foramen in few cases with dumb-bell-shaped tumours.(14) Myelography, computerised tomography (CT) or CT myelography were the investigations for localising these lesions and the pre-operative diagnosis of these lesions was particularly difficult prior to magnetic resonance imaging (MRI).(38) MRI is quite sensitive and found to be the investigation of choice for these lesions.(12,14,28,46) Epidural CA differ from their intramedullary conterparts by the lack of low-signal hemosiderin ring on both T1– and T2-weighted images.(37,46) The T1-weighted images shows homogenous signal intensity similar to spinal cord and muscle or intermediate-signal with respect to neural structures and CSF and on T2-weighted images, lesion has been consistently of high-signal but slightly less than CSF.(5,12,46) On gradient-echo image signal is slightly less bright than fat, similar to what is reported for standard T2-weighted images.(12) Contrast enhancement was moderate, homogenous or slightly heterogenous on T1-weighted images.(12,46) In view of the association of these lesions with cerebral cavernomas MRI of the whole neuraxis to discover other asymptomatic lesions is advocated by Hillman, et al.(14) These lesions are mostly angiographically occult but can occasionally be positive.(13,15,31) The MRI findings needs to be distinguished between other pathological lesions of the spine and the spinal cord which must be considered in differential diagnosis and include schwannoma, meningioma, lymphoma, Ewing’s sarcoma, chordoma, ependymoma, spinal angio-lipoma and disc herniation.(46)

Optimal therapy for epidural lesions is total excision and can grant good outcome.(12-14,31,34,38,46) Whereas cases presenting with acute deterioration or paraplegia show disappointing post-operative outcome.(18,21,27) Incomplete surgical removal because of diffuse bleeding and/or minimal/improper exposure at surgery might result in persistence of clinical symptoms or may lead to recurrence.(7,46) Our patient had total surgical removal of tumour and made a complete neurological recovery and was doing well 5 years after surgery.

Radiotherapy should be considered for unresectable lesions, post-operative residuals and medically unstable patients. Epidural cavernous angiomas lacking bony involvement are often angiographically silent, therefore embolisation plays less prominent role.(13)

Epidural cavernous angiomas are uncommon and potentially curable and grant full neurological recovery if detected early and totally removed surgically, before irreversible neurological damage occurs. These lesions can possibly be diagnosed pre-operatively with the advent of MRI and one should include in the differential diagnosis of patients presenting with spinal cord compression, local back pain or symptoms of radiculopathy.

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