Imaging features in conventional MRI, spectroscopy and diffusion weighted images of hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS)

Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is a rare autosomal dominant disease caused by mutations within the colony stimulating factor 1 receptor (CSF1R) gene. While a small number of reports on imaging findings in routine MRI exist, reported imaging findings in DWI and spectroscopy are scarce, and limited to not genetically proven case reports. We assessed MRI including DWI and MR spectroscopy in six patients with HDLS and two asymptomatic mutation carriers. A total of 13 MRIs were evaluated and a score of the white-matter lesion (WML) load was calculated. The course of MR abnormalities was followed for 6-19 months in four patients and 95 months in one carrier. MRI revealed widespread white-matter lesions of patchy or confluent pattern especially in the frontal and occipital lobe. The pyramidal tract was less affected than the surrounding tissue in all symptomatic patients on conventional T2WI. Three of four cases with DWI showed small dots of diffusion restriction within WML. Spectroscopy showed increased levels of mIns, Cho and lactate while NAA was decreased. Asymptomatic mutation carriers had, for the age of the patients, unusually pronounced unspecific WMLs. No diffusion restriction or alterations in metabolite levels could be detected in asymptomatic mutation carriers. Microbleeds were not found in any patient. Diffusion restriction seems to be a typical imaging pattern visible in patients with active disease progression in HDLS. Spectroscopic findings and the absence of microbleeds differ clearly from reported findings in CADASIL and subcortical arteriosclerotic encephalopathy. While the distribution and character of WMLs in asymptomatic cases remain unspecific they are likely to represent subclinical markers of HDLS.