Clinically Suspected Neurodegeneration in Histiocytic Neoplasms as Causes of Neurologic Decline

Objectives: The aim of this study was to evaluate the causes of suspected neurodegeneration in adults with histiocytic neoplasms. Methods: Patients with histiocytic neoplasms were identified. Inclusion criteria were (1) diagnosis of histiocytic neoplasm; (2) the treating hematologist suspected neurodegeneration; and (3) patients age 18 years or older. Active CNS histiocytic neoplasm was defined as new or enlarging T2 lesions, or gadolinium enhancing lesions on MRI. Results: Neurodegeneration was suspected in 23 of 478 patients. A progressive neurologic disorder was confirmed in 15 of 23 patients and was associated with an underlying active (12/15) or inactive (3/15) histiocytic neoplasm. Of the 8 patients without a progressive neurologic disorder, diagnoses included fixed deficit from histiocytic neoplasm (3/8), depression (2/8), fatigue (1/8), pain (1/8), and stroke (1/8). Of the 3 of 15 patients with progressive neurologic dysfunction and inactive CNS histiocytic neoplasm, all had progressive pontocerebellar dysfunction. Progressive pontocerebellar atrophy on MRI was present in 10 of 13 patients with progressive symptoms, and 2 of 6 patients with no progressive symptoms. Discussion: Progressive neurologic dysfunction in adult patients with histiocytic neoplasms is most frequently because of an active histiocytic neoplasm or nonhistiocytic etiology. A minority of patients have presumed nonneoplastic progressive neurologic dysfunction, primarily associated with pontocerebellar atrophy.