Acute subdural hematoma in Anaplasma phagocytophilum infection: illustrative case.

backgroundEndemic to the northeastern United States, Anaplasma phagocytophilum is an intracellular bacterium that can cause the tick-borne illness human granulocytic anaplasmosis (HGA). While febrile illness, thrombocytopenia, myalgias, and renal and hepatic involvement are common, neurological involvement such as subdural hematoma (SDH) or infarction in HGA is rare. OBSERVATIONS: The authors report the case of a 73-year-old male who presented with febrile illness and then developed acute SDH and acute cerebral infarction in the setting of HGA with associated thrombocytopenia. His condition required emergency surgical intervention due to declining neurological status. LESSONS: This case highlights the rare, but important, consideration of neurological manifestations of HGA. Given the risk of thrombocytopenia seen in HGA, SDH and intracranial hemorrhage should be considered in patients with appropriate risk factors and neurological status changes. In this case, multifocal cerebral ischemic changes and infarction were seen, related to infection and mass effect from a compressive SDH. Management involves multidisciplinary care and centers on treatment of anaplasmosis with doxycycline, further evaluation of co-infections, management of thrombocytopenia, neurosurgical intervention, and rehabilitation for best outcomes and recovery. If treated promptly, prognosis is favorable. https://thejns.org/doi/10.3171/CASE2676.