A 71-year-old male with a past medical history of kidney transplant on immunosuppressive therapy, diabetes, and hypertension presented to the hospital with a 1-day history of headache, nausea, and vomiting. On physical examination, the patient had no focal neurological symptoms, and normal blood pressure. Initial laboratory reports showed an unremarkable cell blood count. Basic metabolic panel, liver function tests, and coagulation panel parameters were all within normal limits. Blood cultures and urine analysis were both negative. Prior purified protein derivative (PPD) tuberculin test and human immunodeficiency virus (HIV) results were negative.
Chest X-ray demonstrated a stable right upper lobe cavitary lesion that had been biopsied twice previously with nondiagnostic results. A head computer tomography (CT) was obtained, which demonstrated a cystic mass in the left cerebellum with perilesional edema [Figure 1]. Further evaluation with contrast enhanced MRI was performed that showed a well circumscribed left cerebellar hemisphere ring enhancing mass on T1 sequences with restricted diffusion, mass effect, and perilesional edema [Figure 1]. Differential diagnosis included pyogenic abscess (bacterial or fungal), neurocysticercosis, cystic glioma, or other cystic malignant/metastatic process.
The patient underwent a left posterior fossa biopsy and drainage. The lesion was well encapsulated with a frankly purulent center. Numerous acid fast bacilli were seen on acid fast stain, and cultures returned positive for mycobacterium tuberculosis [Figure 2]. Cerebrospinal fluid (CSF) cultures were also obtained, which were negative. Microbiology revealed pan sensitive mycobacterium tuberculosis and the patient was started on rifampicin, isoniazid, pyrazinamide, ethambutol (RIPE), and B6.
Follow-up MRIs were obtained 1, 4, 9, 11, and 14 months [Figures 3 and 4]. During this time, the patient was seen monthly, and had continued to show clinical improvement with treatment. After 6 months, ethambutol had been removed from the treatment regimen. Treatment with rifampicin, isoniazid, and pyrazinamide was continued in order to maximize CNS penetration, and it was noted on the 9-month MRI that the tuberculosis abscess had grown in size from 2.0 x 2.0 x 2.2 to 2.5 x 3.3 x 2.3 cm [Figure 3]. While the abscess had grown in size at 9 months, the amount of perilesional edema had decreased [Figure 4b]. At this time the patient's neurologic examination and symptoms were stable, and given the continued clinical improvement, and pan sensitive cultures, the drug regimen was not changed. Due to the increase in size, vigilant surveillance with frequent clinic visits was pursued. The 11-month follow up MRI showed that the abscess size was decreased to 1.5 x 2.2 x 1.2 cm, and on month 14, the abscess had nearly resolved [Figure 3].