Neuroleukemiosis: an unusual cause of peripheral neuropathy.

Leukemia may initially present as a peripheral neuropathy, leading to a delay in diagnosis. Leukemic infiltration of peripheral nerves, or neuroleukemiosis (NL), is exceedingly rare, with no established diagnostic or therapeutic guidelines. Five cases are presented. All patients were men with a median age of 68 years (range 46-72). Three patients had acute myeloid leukemia (AML) and two had chronic lymphocytic leukemia (CLL). In two patients, leukemia presented with peripheral nerve involvement and both were found to have positive cerebrospinal fluid (CSF) cytology, making the diagnosis AML, despite negative bone marrow and peripheral smear. All patients had painful, progressive, motor and sensory deficits. Clinical patterns were mononeuropathy (n =1), multiple mononeuropathies (n =1) and plexopathy (n =3). Magnetic resonance imaging (MRI) detected mass lesions in 4/5 cases, with avid fluorodeoxyglucose (FDG) uptake on positron emission tomography (PET) useful in all of these for following clinical disease progression. Three cases of nerve biopsy were performed, two of which were diagnostic of leukemic infiltration. Radiation treatment rapidly relieved pain in patients with mass lesions, in combination with chemotherapy. Four patients had disease relapse, four systemic and one also in peripheral nerves. These cases are discussed in the context of the broader literature.