Tumefactive acute disseminated encephalomyelitis complicating human swine influenza (H1N1)

Tumefactive Acute Disseminated Encephalomyelitis

Tumefactive demyelination is a phenomenon involving the radiographic resemblance of an acute demyelinating process in the central nervous system to neoplasia. Although this has been described and characterized for multiple sclerosis, it has been reported in a few cases in patients with acute disseminated encephalomyelitis (ADEM) within the past decade. While it may be challenging to establish a diagnosis of tumefactive ADEM according to clinical and radiological data alone, a thorough review of the clinical history and following the patient over time can be supportive of the same. The principal diagnostic confounds include neoplastic disease and a first attack of multiple sclerosis. A definitive diagnosis can be made by biopsy, which reveals perivenular demyelination and mononuclear cell infiltration in ADEM, in contrast to confluent plaque-like areas of demyelination in patients with multiple sclerosis. Histopathologic evidence of neoplastic disease includes characteristic features, including nuclear atypia and polymorphism, cellular hyperproliferation, mitoses, necrosis, endothelial proliferation, rosettes, and/or pseudorosettes. ADEM responds excellently to treatment with corticosteroids and is monophasic, with recurrence occurring infrequently. We review the literature on tumefactive ADEM and discuss the clinical manifestations, imaging characteristics, and histopathologic findings used to distinguish it from other conditions.

The hidden burden of influenza: A review of the extra-pulmonary complications of influenza infection

Severe influenza infection represents a leading cause of global morbidity and mortality. Although influenza is primarily considered a viral infection that results in pathology limited to the respiratory system, clinical reports suggest that influenza infection is frequently associated with a number of clinical syndromes that involve organ systems outside the respiratory tract. A comprehensive MEDLINE literature review of articles pertaining to extra‐pulmonary complications of influenza infection, using organ‐specific search terms, yielded 218 articles including case reports, epidemiologic investigations, and autopsy studies that were reviewed to determine the clinical involvement of other organs. The most frequently described clinical entities were viral myocarditis and viral encephalitis. Recognition of these extra‐pulmonary complications is critical to determining the true burden of influenza infection and initiating organ‐specific supportive care.

Severe post-influenza (H1N1) encephalitis involving pulvinar nuclei in an adult patient

Neurological complications of H1N1 infections are mostly found in children, but rare cases of acute encephalopathy and post-infectious encephalitis such as acute disseminated encephalomyelitis (ADEM) have been described in adults. We report a case of an adult presenting with a progressive and severe encephalopathy that developed after H1N1 respiratory infection resolution. Cerebrospinal fluid (CSF) analysis was normal, including negative PCR for herpes simplex virus, H1N1, influenza B and JC virus, and absent oligoclonal IgG bands in CSF and serum. Initial CT scan was normal, but later MRI showed posterior multifocal leucoencephalopathy with pulvinar sign. The delayed neurological findings together with the ancillary investigation, namely the MRI pattern with both grey and white matter involvement, raised the possibility of a post-infectious process, rather than an acute encephalitis. Despite aggressive immunotherapy, the patient experienced severe neurological sequelae. Early recognition of ADEM manifestations by those dealing with H1N1 infection is important as early immunotherapy may improve the prognosis.