Intramedullary tubercular abscess with syrinx formation.

Intramedullary spinal cord tubercular abscess with involvement of whole cord is a rare entity that too with syrinx formation following disseminated meningitis. Accurate diagnosis requires a high index of suspicion with clinical history and imaging features for a favorable outcome. Here-in we present a similar case with tubercular etiology which was also associated with syrinx formation and has not been reported previously in the literature up to the author's knowledge.

Introduction

Intramedullary spinal cord tubercular abscess with involvement of whole cord is a rare entity that too with syrinx formation is even rarer.[12] Till date only 83 cases of intramedullary abscess of tubercular etiology have been reported in the literature with only six cases of holocord and with only one case of syrinx since the original description by Marinesco in 1916.[34] Besides an adequate clinical history, a high index of suspicion and imaging features helps in diagnosis.

Case Report

A 4-year-old boy presented with fever and acute flaccid paralysis for the past 6 months. After a detailed physical examination, provisional diagnosis of complicated meningitis was made. His lumbar puncture examination revealed few lymphocytes and increased protein content. The patient was given antibiotic but it was not optimally effective. Finally, the patient was subjected to Magnetic resonance imaging (MRI) of the brain and spine to determine the cause.

MRI investigation revealed expansion of cord and dilated central canal with altered signal intensity in cord parenchyma ranging from the cervicomedullary junction to conus medullaris, which was iso- to hypointense on T1, heterogeneously hyperintense on T2WI. T1 fat suppressed Gadolinium-enhanced sequences revealed peripheral enhancement with central hypointense areas from D6 vertebral level to conus medullaris consistent with inflammatory collection [Figures 1 and 2]. It also showed significant syrinx formation from D1 to D6 vertebral level with evidence of altered signal intensity in cord parenchyma [Figure 3]. His brain MRI also revealed significant communicating hydrocephalus.

Figures 1 and 2

Contrast-enhanced Sagittal T1-weighted MRI showing intramedullary abscess with rim enhancement extending from D6 to conus level

Figure 3

Sagittal T2-weighted sequence showing expansion of cord and dilated central canal from cervicomedullary junction to C7 with hyperintense signals from intramedullary portion of cord signifying liquefaction from D1 to D6 level

Following MRI, the patient underwent surgery for drainage and confirmation of the etiology. Partial laminectomy was performed and through a midline myelotomy intramedullary abscess was drained. The spinal cord which was distended became lax after the surgical procedure. The necrotic pus-like tissue collected was sent for culture and histopathological examination. Histopathological examination showed the presence of chronic inflammatory cells with caseating epithelioid cell granuloma and ZN staining was also performed on sections which showed AFB positive bacilli [Figures 4 and 5]. Culture showed acid fast bacilli confirming tubercular nature of the lesion. Postoperative recovery was uneventful with rapid improvement of clinical symptoms and the patient was discharged with ATT with an advice for regular follow-up.

Figure 4

H and E stain shows characteristic tubercular lesion depicting epithelioid cell granulomas along with Langhans giant cell surrounded by rim of lymphocytes and central focal necrosis (40×)

Figure 5

Ziehl–Neelsen staining showing AFB-positive bacilli (100×)

Discussion

Intramedullary tuberculosis is almost always secondary to pulmonary tuberculosis with rare exception as isolated extrapulmonary forms. Isolated involvement of spinal cord by tuberculoma or abscess is extremely rare and that too involvement of whole cord has been reported in very few cases.[1] After the first documentation by Hart in 1830, only 83 cases of intramedullary abscess have been reported in the world literature.[23] Syrinx formation secondary to inflammation is another rare occurrence where the literature is scanty. A literature survey has documented only one case that too with inflammatory arachnoiditis since the description of the first case of “TB caused” syringomyelia by Marinesco in 1916.[4]

This entity is usually seen in children and is more common in male patients. A total of 40% of the abscesses occur in first two decades with 27% occurring before the age of 10 years.[5] The incidence of spinal cord abscesses is significantly low compared to brain abscess. This has been attributed to its peculiar blood supply and the lower volume of spinal cord. These abscesses can be solitary or multiple or can involve the entire cord[15] as seen in our case. The most common location of solitary abscess formation in the cord is the thoracic region.[1] Clinical features range from back pain, fever and tenderness in acute stage to chronic symptoms such as progressive paraplegia, numbness and paresthesia.[67] Various case reports have described the differing and varied clinical presentations.

Diagnosis of spinal cord tubercular abscess can be made from positive tissue culture or detection of acid fast bacilli but a previous study has shown that in most cases culture remains sterile.[8] Commonly isolated organisms are staphylococcus and streptococcus in developed countries and mycobacterium in developing countries.[3910] Viruses, fungi, cysticercus, listeria, toxoplasma, and brucella may also be isolated.

Radiologic investigations are unlikely to be conclusive. However, imaging especially MRI is relatively more sensitive which helps in detection, precise localization, and extent of the abscess. MRI demonstrates the hypointense signal on T1W and the hyperintense signal on T2W sequences. On postcontrast fat suppressed T1 sequence peripheral contrast enhancement around the abscess appearing as classical "ring sign" is typical of an abscess.[11-13] Similar findings were noted in our case which revealed peripheral enhancement ranging from D6 to conus medullaris [Figures 1 and 2]. Besides this, a proximal syrinx formation was also observed in our case as seen in the T2W sagittal image [Figure 3] which has not been reported previously. MRI is therefore a radiological study of choice for both diagnosis and management.

Treatment of intramedullary abscess includes medical therapy, i.e., specific antituberculous chemotherapy without surgical evacuation. Surgical evacuation is considered if the lesion is large with rapid deterioration of neurological status as in our case. Appropriate antituberculous chemotherapy after pus drainage, surgical excision, and culture usually gives a favorable outcome.[314]