Intradural extramedullary cysticercal abscess of spine.

Neurocysticercosis (NCC) is one of the most common parasitic diseases affecting the central nervous system. Typically spinal NCC involvement has a concomitant cranial involvement. Spinal involvement by NCC, either intramedullary or extramedullary is very uncommon. The authors report a case of D12-L1 intradural extramedullary lesion in a 38-year-old female patient who presented with complaints of back pain and weakness of lower limbs. She underwent laminectomy and excision of the lesion. Histopathology revealed extramedullary cysticercal abscess. Post-operatively she was treated with albendazole. She had a successful recovery post-operatively and at 8 months follow up had no neurological deficits. This current case presents a very rare case of cysticercal abscess of dorsolumbar spine, without any evidence of cranial involvement. This report is to reemphasize the importance of including NCC as a differential diagnosis in intradural extramedullary lesion at the conus level in endemic areas like India.

INTRODUCTION

Neurocysticercosis (NCC) is the most common parasitic infection affecting the central nervous system (CNS).[12] Cysticercuscellulosae, the larval form of Taenia-solium causes human NCC. Pigs are the intermediate host while humans are definite host.[12] NCC typically involves the brain parenchyma, intracranial subarachnoid space or ventricular system and is most often has a self-limiting course.[3] NCC affecting the spine is rare with an incidence of around 1-3%.[4-6] Most of these spinal cases of NCC described in the literature have a concomitant cranial involvement.[5] Isolated spinal involvement without cranial lesions is rare. Timely diagnosis and appropriate management is warranted in these cases due to the natural small confines of the spinal canal and its potential to cause irreversible neurological deficits.[37-9] This current case presents a very rare case of cysticercal abscess of dorsolumbar spine.

CASE REPORT

A 38-year-old female patient came with complaints of insidious onset, slowly progressing back pain with pain radiating anteriorly to abdomen of one week duration associated with weakness and numbness of both lower limbs. Her bowel and bladder were normal. On examination she had bilateral lower limb paresis of 4/5 (MRC Medical Research Council grading) and decreased sensations below L2 dermatome. The lumbosacral spine magnetic resonance imaging (MRI) showed a mixed intensity, intradural extramedullary lesion at D12-L1 level measuring about 11.4 × 11.2 × 22.8 mm displacing the conus and cauda with heterogenous enhancement with contrast [Figure 1]. She underwent D12-L1 laminectomy, biopsy, debulking, and decompression of the cord. Intraoperatively there was evidence of group of dilated vessels which were followed into a lesion that appeared to be like schwannoma at some areas and epidermoid at other areas. A major portion of lesion was dissected. At the cranial end of the lesion there was a sudden gush of yellowish pultaceous material and a diagnosis of inflammed epidermoid was made intraoperatively. Histopathology showed a well-formed abscess adjacent to which a cystic structure was thrown into folds. Close up view of the abscess showed fibrocollagenous wall and dense aggregates of large foamy histiocytes admixed with lymphocytes. The cystic structure revealed wall of cysticercal cyst with outer well preserved undulating tegumentary layer with inner zone of subtegumentary cytons and loose reticular layer with excretory/secretory ductules. No scolex was identified [Figure 2]. Culture of the cyst content was negative for bacterial growth. A final diagnosis of cystericercal abscess was made. Post-operatively she was given a course of albedazole and steroids for a period of 8 weeks. She had relief from her back pain and had improvement in her paresis. At a follow up period of 8 months she has no neurological deficits.

Figure 1

Magnetic resonance imaging lumbosacral spine showing a T1W isointense lesion intradural extramedullary lesion at D12-L1 level measuring about 11.4 × 11.2 × 22.8 mm displacing the conus and cauda (a and b). On contrast (c and d) there is heterogenous enhancement with hypointense center and peripheral enhancement

Figure 2

Histopathology revealed a well formed abscess adjacent to which is a cystic structure thrown into folds (a, asterix). Close up view of the abscess wall (b, w) shows dense aggregates of large foamy histiocytes admixed with lymphocytes. The cystic structure on close up view (c) reveals wall of cysticercal cyst (asterix) with outer well preserved undulating tegumentary layer with inner zone of subtegumentary cytons and loose reticular layer with excretory/secretory ductules. No scolex identified (a-c: H and E stain, magnification-scale bar)

DISCUSSION

The first description of human NCC was given by Paranoli Rumi in 1550.[15] NCC involving the spine was first reported by Rockitansky in 1856.[4] NCC is the most common parasitic infestation affecting the CNS in humans.[1] NCC affecting spine is very rare with less than 200 cases being reported.[1] Rossitti et al.,[10] reported an incidence of 1.4% in 205 cases of NCC.. The incidence of spinal NCC is reported to be around 1.5-3.0% in the literature.[111] Cysticercal abscess is very rare. This is the first case of spinal cysticercal abscess documented. The pathogenesis of abscess formation can be attributed to degenerating cysticercosis. Most of the cases of spinal NCC occur in presence of coexisting cranial NCC. Isolated spinal involvement constituting a minority of cases.[112] Various theories for this have been proposed for rare occurrence of the spinal NCC, like CSF cerebrospinal fluid reflux at craniovertebral junction preventing the spinal dissemination by propelling the floating cysts back to intracranial space[13] or retrograde flow of these larvae through valveless epidural venous plexus due to variations in intra-abdominal and intra-thoracic pressure.[14] Though the larval migration is prevented by CSF reflux, epidural venous portal remains the most important mode of entry for cysticercal larvae to the spinal territory[1113] as seen in our case. Subarachnoid space is reported to be the most common location, seen in 80% of the spinal cysticercosis cases followed by intramedullary location in remaining 20%.[1315] Extradural location of spinal NCC is very rare.[13] The sign and symptoms produced by spinal NCC depends on various factors such as size, location, spinal level, and presence or absence of arachnoiditis/inflammation due to cyst degeneration.[13816] They can present with mass effect, inflammatory reaction causing arachnoiditis and meningitis or obstruction of subarachnoid pathways.[1] At times myelopathy due to cord compression leading to progressive weakness has also been reported.[1117] Extramedullary NCC of lumbar region tends to give rise relatively slow and insidious onset of symptoms.[15] Cyst degeneration evokes an intense inflammatory reaction which may induce severe symptoms.[1] Live cysts cause less inflammation and therefore are easy to excise surgically.[18]

MRI is the diagnostic modality of choice for evaluating the spinal NCC. Rahalkar et al.,[19] described the various stages of disease, i.e., vesicular stage, colloidal vesicular stage, granulonodular stage, and calcified nodular stage depending on MRI findings. Despite the classical description of different stages of NCC, it is important to remember that all the stages of cysticercosis larva can be present simultaneously. In our patient the lesion was seen at D12-L1 level. On MR imaging these lesions appears hypointense on T1W MRI and hyperintense on T2WI images with surrounding edema and ring enhancement on post-contrast T1W MRI.[9122021] In our patient the lesion was isointense to cord on T1W images with heterogeneous contrast enhancement. CSF ELISA can confirm the diagnosis of NCC with a high sensitivity of 87% and specificity of 97%.[21] However, the only definitive method of confirming the diagnosis is by excision and histopathological examination.[422] In our case though intraoperative diagnosis was inflamed epidermoid, but histological diagnosis was cysticercal abscess. In the absence of a characteristic scolex and absence of cerebral involvement as in our case, the diagnosis is difficult to arrive at considering the rarity of this lesion in spine.[2023]

The typical histopathological findings of NCC are presence of dead or active translucent cysts with eosinophilic lining. The cysts are usually surrounded by clear fluid and chronic inflammatory cells including neutrophils, eosinophils, and giant cells. In our case the cyst was surrounded with fibrocollagenous outer wall infiltrated with dense inflammatory cells, large foamy histiocytes, plasma cells admixed with lymphocytes, and neutrophils confirming the features of abscess formation. Due to rarity of spinal NCC, no definitive guidelines for treatment were proposed.[32023] Mohanty et al.,[2425] believe that the spinal NCC represents focal manifestation of a systemic disease and recommend medical therapy in all patients with spinal NCC. The efficacy of antihelminthic therapy in cases of spinal cysticercosis has been documented by various authors with resolution of neurological deficits.[31623] The first line of medical management includes albendazole and praziquental along with steroids and strict neurological monitoring.[4] Surgical decompression is warranted if clinical deterioration is observed during the pharmacotherapy.[1] Surgery is indicated in patients who present with acute onset of symptoms and in those where the diagnosis is in doubt to eliminate the compressive element and to get histopathology confirmation of the diagnosis. Early surgery provides maximal chances of recovery before any irreversible cord changes take place.[13122526] Dense arachnoiditis can cause difficulty in excision in extramedullary lesion.[11727] The aim should be maximum possible excision without compromising the neurological status. Various measures like sharp dissection, gentle irrigation and Valsalva maneuvers have been suggested to assist in cyst extripation and reducing post-operative complications.[11727] Re-establishment of CSF flow should be considered if CSF block is suspected due to arachnoiditis.[1] Following complete excision the outcome may be poor due to parenchymal gliosis, pachyleptomeningitis causing cord degeneration, and vascular compromise.[13]

CONCLUSION

This is the first report of cysticercal abscess affecting the spinal canal. Spinal NCC is a very rare manifestation, it should be considered in the differential diagnosis in patient populations in endemic areas with symptoms suggestive of a spinal mass lesion. The definitive method of confirming the diagnosis is by excision and histopathological examination. Though medical management can be tried as first line of management, a high clinical suspicion is warranted to operate if clinical deterioration is observed.