In a patient with tremor, bradykinesia, dizziness, and headache, whose brain MRI shows bilateral periventricular and deep white‑matter hyperintensities, subtle diffusion restriction, and thinning of the posterior corpus callosum, what is the likely diagnosis and what further evaluation is recommended?

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CSF1R-Related Leukoencephalopathy (Adult-Onset Leukodystrophy)

Based on the imaging findings—bilateral periventricular and deep white matter T2/FLAIR hyperintensities extending to subcortical regions, persistent diffusion restriction in corona radiata and posterior parieto-occipital white matter, and thinning of the posterior corpus callosum—the most likely diagnosis is CSF1R-related leukoencephalopathy, and you must proceed immediately with CSF1R gene sequencing. 111

Why This Diagnosis Fits

The imaging pattern is highly characteristic of CSF1R-related leukoencephalopathy based on the 2022 systematic review of 195 cases 111:

  • White matter distribution: Frontoparietal and periventricular hyperintensities (present in 81% of cases) extending to deep white matter (23% of cases) and occipital lobes (7% of cases) 11
  • Corpus callosum involvement: Thinning of the posterior body is characteristic, reported in 29% of cases as callosal atrophy 11
  • Persistent diffusion restriction: The subtle high signal on DWI in bilateral corona radiata and subcortical posterior parieto-occipital white matter is a hallmark finding—diffusion restriction occurs in 27% of cases and persists for months to years, which is seldomly seen in other neuroinflammatory or neurodegenerative disorders 111
  • T1 hypointensity: Areas showing internal low signal on T1WI correspond to white matter hypointensities characteristic of this disease 11

Clinical Correlation

The patient's symptoms align with CSF1R-related leukoencephalopathy:

  • Tremor and bradykinesia: Movement disorders including parkinsonism are well-documented in this condition 11
  • Median onset age: 41 years (IQR 17 years), with women presenting slightly earlier at 40 years 1
  • Progressive nature: The disease shows ongoing white matter lesion progression and brain atrophy on follow-up imaging (47% of cases over median 3 years) 11

Critical Diagnostic Steps

1. Genetic Testing (Priority #1)

Order CSF1R gene sequencing immediately. This is the definitive diagnostic test for CSF1R-related leukoencephalopathy (also known as adult-onset leukoencephalopathy with axonal spheroids and pigmented glia, or ALSP) 111.

2. Additional Imaging to Consider

  • Brain CT without contrast: Look for calcifications—present in 75% of cases, typically in a "stepping-stone pattern" (19%) or "spotty calcifications" (16%) in frontal white matter adjacent to frontal horns, periventricular areas, or pericallosal regions 11
  • Contrast-enhanced MRI: While gadolinium enhancement is rare in CSF1R-related leukoencephalopathy (only 1 of 195 cases showed enhancement), it helps exclude inflammatory/autoimmune mimics 11

3. Functional Imaging (If Available)

  • FDG-PET: Shows cortical hypometabolism in prefrontal, frontal, and parietal regions (57% of cases) 11
  • DaTscan: May show normal findings or reduced putaminal uptake, helping differentiate from primary Parkinson's disease 11

Key Differential Diagnoses to Exclude

The imaging pattern requires excluding these mimics 11:

  1. Multiple sclerosis: Look for ovoid lesions perpendicular to ventricles, gadolinium enhancement, and spinal cord involvement (your patient has no spinal cord demyelination) 2
  2. CADASIL/CARASIL: Typically shows temporal pole involvement and lacunar infarcts—not prominent here 2
  3. Vascular parkinsonism: Would show lacunar infarcts, microbleeds, and involvement of substantia nigra/nigrostriatal pathway—not the diffuse white matter pattern seen here 3
  4. Vanishing white matter disease: Usually presents earlier (though adult-onset exists) and shows more confluent white matter loss 4

Common Pitfalls to Avoid

  • Don't dismiss persistent diffusion restriction as acute stroke: The long-lasting DWI hyperintensity (months to years) is pathognomonic for CSF1R-related leukoencephalopathy, likely representing fluid trapped between degenerating myelin layers 11
  • Don't confuse with normal aging changes: The extensive subcortical involvement, corpus callosum thinning, and diffusion restriction far exceed age-related white matter hyperintensities
  • Don't wait for contrast enhancement: Unlike MS or other inflammatory conditions, CSF1R-related leukoencephalopathy rarely enhances 11

Prognosis and Management Implications

This diagnosis carries significant implications for morbidity and mortality:

  • Progressive disease: White matter lesions and brain atrophy worsen over time in 47% of cases 11
  • No cure currently available: Management is symptomatic only 4
  • Genetic counseling essential: Autosomal dominant inheritance pattern requires family screening 11
  • Symptomatic treatment: The patient may benefit from levodopa/carbidopa for parkinsonian symptoms, though long-term efficacy is uncertain 4

The absence of spinal cord involvement (normal whole spine screening) further supports CSF1R-related leukoencephalopathy over MS, which commonly affects the spinal cord 1.

References

3
Research

Vascular Parkinsonism: deconstructing a syndrome.

Movement disorders : official journal of the Movement Disorder Society, 2015

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