Nocardiosis is an uncommon infection which occurs due to aerobic Actinomyces species of Nocardia, and Nocardia is ubiquitous in the environment. The infection mainly occurs by inhalation, and also transmitted through cutaneous disease, insect bite, trauma, surgery, and vascular catheters. Nocardia expresses to have a distinct tropism towards the neural tissue. Solitary abscess denotes the most common appearance in the central nervous system (CNS), accounting for 1% to 2% of all cerebral abscesses. Nocardia farcinica seems to be more virulent than other subspecies, since the infection may cause disseminated lesions, tend to relapse and have a higher antibiotic resistance (especially to third generation cephalosporins). Furthermore, Nocardiosis usually affects immune compromised patients.
A recent research on 66-year-old immune proficient man having hypothyroidism in his medical history along with diabetes mellitus was referred for a 6-week history of night sweats and progressive fatigability followed by irregular diplopia, memory disturbance and loss of balance. Fever, headache, vomiting and seizures were not been reported. The neurological examination of the afebrile patient was conducted as he was admitted and revealed disorientation, drowsiness, left facial nerve palsy, dysconjugate eye movements, motor aphasia, dysmetria at the finger-to-nose and heel-to-shin maneuvers bilaterally, dysdiadochokinesia and severe gait ataxia. cMRI showed multiple supratentotial lesions (in the right pre and post-central gyrus, left frontal and temporal lobe bilaterally) and a wide nodular heterogeneous hyperintensity on FLAIR images in the left midbrain and pons, with the involvement of cerebellar hemisphere and the basal ganglia of the left side and an adjacent mass effect. Maximum of the lesions displayed partially diffusion restriction and ring gadolinium enhancement. Mild pachymeningeal thickening and enhancement were also identified. A primary diagnosis of tumor was made and the patient started on dexamethasone.
To one side from the diabetes, history did not specify immune deficiency, and travel, work and exposition history were unremarkable. Extensive laboratory data only showed a slightly decreased white blood cell count, but the absolute values were typical, serum immunoglobulin levels were within normal range and human immunodeficiency virus serologic test was negative. Biopsy of the left temporal lobe lesion showed the presence of an abscess comprising of methylamine silver staining filamentous structures, resembling Nocardia spp. The microbiological evaluations on brain tissue and blood were positive for Nocardia farcinica. The antibiotic susceptibility revealed a cefotaxime-resistance. Because of hydrocephalus occlusus caused by the space-occupying brain stem lesion the patient required temporary external ventricular drainage. The patient was treated with intravenous imipenem (1 g qid) and cotrimoxazole (960/4800 mg daily) was administered for one month with substantial improvement of neurological conditions. The patient was conscious after four weeks of treatment but disorientated, had recovered from diplopia and facial nerve palsy, while aphasia, dysmetria and gait had substantially improved. The one month follow-up cMRI showed a regression of supratentorial and brain stem lesions.
The report presented a case of primary multiple brain abscesses due to N. farcinica in an immune competent patient. CNS norcardial infections visible like a single abscess, multiple brain or spinal cord lesions, diffuse cerebral inflammation, and meningitis mimicking neoplasms, vasculitis, and stroke. The estimated mortality rate for Nocardia brain abscess are 55% and 20% in immune compromised and immune competent patients, respectively; however, these rates may rise for multiple abscesses and if the infection is due to the subspecies N. farcinica. Nocardial brain abscesses are not common and Nocardiosis in immune competent individuals is even less frequent, being the infection usually observed in immune compromised hosts. Symptomatology could be insidious, variable and without fever or other clear infective symptoms, delaying diagnosis and treatment. Antibiotics perhaps are maintained for up to 12 months to prevent relapses. In conclusion, in spite of the low incidence, no cardial infection should be evaluated in the differential diagnosis of cerebral lesions in both immune deficient and immune competent patients, as early identification and suitable treatment are very critical for a promising outcome of this potentially life-threatening infection.