Acute disseminated encephalomyelitis.
This case highlights several important principles to both the clinical neurologist as well as the neuropathologist. Initially, highest on the differential was opportunistic infection, lymphoma, or demyelination. Due to concern for CNS toxoplasmosis, the patient was empirically treated with pyrimethamine and sulfasalazine. Given the lack of laboratory evidence and clinical improvement to support this treatment strategy, tissue diagnosis was pursued. Just prior to this time, the patient worsened clinically to where he had anarthria, severe dysphagia and left hemiplegia. After the pathology was reviewed and a tissue diagnosis made, the course of treatment was completely changed and he was treated with intravenous methylprednisolone followed by an oral prednisone taper and five rounds of plasma exchange. Follow-up MRI showed complete resolution of contrast enhancement with stability of the T2/FLAIR signal. Clinically, he became more interactive and verbal with improvement of his left hemiparesis.
There are numerous neurologic manifestations of HIV/AIDS both intrinsic to the infection as well as the immunocompromised state that is seen in other patients, such as transplant recipients who are iatrogenically immunosuppressed. A history of immunodeficiency is salient to the astute clinician and widens the differential considerably. Notably, while this patient did technically meet criteria for AIDS, his CD4 count was on the borderline.
Toxoplasmosis is the most common CNS parasitic opportunistic infection in AIDS patients and the most common AIDS-defining illness in the CNS. On MRI, it frequently presents with multiple ring-enhancing lesions, particularly in the grey-white junction and the basal ganglia. Approximately 95% of these patients will have anti-toxoplasma IgG antibodies. Primary CNS lymphoma is a form of non-Hodgkin lymphoma and is second only to toxoplasmosis for mass lesions in the brains of AIDS patients. On neuroimaging, single or multiple contrast enhancing lesions are present and can be ring patterned or homogeneous (2).
ADEM is a disease of acute multifocal demyelination in the CNS that typically follows an infectious illness and presents heterogeneously. Full recovery may occur and treatment consists of therapies such as steroids, IVIg, and plasma exchange (3). ADEM may present with ring-enhancing lesions and can mimic CNS toxoplasmosis or lymphoma (4). There are rare case reports of ADEM in patients with HIV/AIDS but the nature of this relationship needs to be further elucidated (1).
We present a rare case of pathologically confirmed extensive demyelination with multiple incomplete ring-enhancing lesions in a man with AIDS. This case demonstrates that while immunocompromised patients have an expansive differential including opportunistic infections and malignancies, they are also prone to the diseases that immunocompetent patients are. As the prognosis and management may differ vastly, considering all diagnostic possibilities is important. In this case, brain biopsy was instrumental in making the diagnosis and embarking on a completely different treatment strategy
Contributed by Peter Kang, MD, Robert E. Schmidt, MD, PhD, Sonika Dahiya, MD, Arun S Varadhachary, M, PhD