Teaching Case

19-year-old male patient presented to neurology clinic of our hospital with complaint of sudden onset right-sided body weakness. On examination his higher motor function and cranial nerves were intact. There was numbness of right side of body with upgoing right planter reflex. His past history was significant for migratory polyarthralgias.

Pre and post contrast images of CT scan of head show multiple hypodense lesions in both cerebral hemispheres with surrounding edema demonstrating intense post contrast enhancement.
MRI brain demonstrated T1 hypo and T2 hyperintense lesions showing surrounding edema and intense post contrast enhancement.
CT thorax showed an essentially non enhancing mass, predominantly in posterior mediastinum invading the left atrium, left pulmonary veins and left main braochus. The mass was seen crossing the midline and also encasing the descending thoracic arota. Multiple thrombi were also noted in both left atrium and ventricle.

Mediastinal masses are classified according to location. common anterior mediastinal masses include Thymoma Teratoma Thyroid related masses and Lymphoma. Middle mediastinal masses include Lymphoma Necrotic nodes Infections Duplication cysts and Anomalous or enlarged vessels. Posterior mediastinal masses include Neurogenic tumors, Extramedullary hematopoiesis, Duplication cysts and Anomalous/enlarged vessels.[1] Infections, bronchogenic carcinoma and haemorrhage tends in involve multiple mediastinal compartments.[1] Differentiating mediastinal tumors and infections and be challenging at times and usually end up requiring histopathological diagnosis. Infective mediastinal masses are rarely seen in immunocompetent patients and are frequently invasive. Patients usually present with secondary signs of mediastinal disease like mediastinitis, septic shock, [3] signs of SVC obstruction, pulmonary edema [2] and peripheral emboli to brain if there is concomitant cardiac involvement. Contrast enhanced CT is considered the investigation of choice.
Imaging findings include a non-enhancing invasive mass which does not respect the mediastinal compartments. The leading diagnostic cue is the involvement of vascular structures like SVC and pulmonary veins. Obstruction of pulmonary veins may lead to development of pulmonary edema.[2] MRI is used to confirm cardiac invasion and to delineate anatomy.[2] Although imaging may suggest the diagnosis, biopsy is usually obtained to confirm the diagnosis and to device the treatment plan. Both surgical resection and anti fungal medication are used in treating the disease. our patient denied the surgical option and opted for anti-fungal medication to which he responded well. However his neurological deficit persisted although there was mild improvement. Despite significant advances in thoracic surgery and development of improved antifungal medications, prognosis of mediastinal fungal infections and not increased accordingly.[4] The main teaching point this case gives us is that atypical infections should be suspected in multi-compartmental mediastinal masses irrespective of the immunological status of the patient.
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