General description

CLIPPERS, an acronym for Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids, is a form of encephalitis characterized by subacute, progressive ataxia and dysarthria. This condition is distinguished by its lymphocytic infiltration, primarily involving CD3 and CD4 positive T-cells, around vessels without the presence of monoclonal lymphocyte proliferation, granulomas, or giant cells. Additionally, the vessels themselves do not show signs of inflammatory changes. Some cases are known to have decreased lymphocytes, elevated serum IgE, and positive autoantibodies.

The hallmark of CLIPPERS is its marked responsiveness to steroid treatment, which significantly alleviates symptoms. Initially conceptualized as a unique form of brainstem encephalitis, the condition has undergone reevaluation due to cases that have progressed to malignant lymphoma. This progression has raised concerns that CLIPPERS might sometimes represent an early stage of lymphoma.

Radiographic features

The imaging findings for CLIPPERS prominently feature symmetric contrast effects surrounding vessels, particularly noticeable in the pons, medulla oblongata, and extending to the cervical and thoracic spinal cord. The pattern of these contrast enhancements is often described as mottled to dotted. Alongside these contrast effects, there is usually a corresponding high signal on T2WI in the same regions, although this high signal is often not consistently present.

Additionally, while similar imaging findings can occur in other brain regions, the intensity and prominence of these changes tend to diminish the further they are from the pons and medulla oblongata.