Crested Cap

Crested Cap. It is a distinctive neuroimaging finding characterized by a hyperintense signal along the crest of a cerebral gyrus, most commonly observed on FLAIR MRI sequences. This radiological sign is associated with a specific pattern of cortical pathology and is often identified in the context of certain neurological conditions. The presence of a Crested Cap is considered a valuable diagnostic clue by neuroradiologists and neurologists, guiding further clinical evaluation and management.

Description

The Crested Cap appears as a linear or curvilinear bright signal selectively involving the apex of a gyrus, contrasting with the normal signal of adjacent gray matter and underlying white matter. It is best visualized on FLAIR images, a MRI technique that suppresses CSF signal to improve lesion conspicuity. This finding is typically seen in regions like the frontal or parietal lobes. The sign was first systematically described in studies of Creutzfeldt-Jakob disease but has since been recognized in other disorders. Its specificity stems from its correlation with particular histopathological changes at the crest of the involved cortical fold.

Causes

The Crested Cap is primarily caused by pathological processes that preferentially affect the most superficial layers of the cerebral cortex at the gyral crown. In Creutzfeldt-Jakob disease, it is linked to the deposition of abnormal prion protein and associated spongiform degeneration. Other causes include certain forms of focal cortical dysplasia, particularly Type II variants, where it may reflect abnormal neuronal architecture and glial proliferation. It has also been reported in some cases of chronic epilepsy related to hippocampal sclerosis and in a subset of patients with autoimmune limbic encephalitis. The common thread is a focal disruption of the normal laminar structure of the cortex.

Diagnosis

Diagnosis is primarily radiological, relying on expert interpretation of brain MRI. The FLAIR sequence is essential for detection. Differential diagnosis includes other cortical hyperintensities such as those seen in acute ischemic stroke, encephalitis, or PRES. Correlation with clinical history from a neurologist is critical; for instance, a rapidly progressive dementia suggests CJD, while drug-resistant seizures point toward focal cortical dysplasia. Advanced techniques like diffusion-weighted imaging or PET scans may provide supporting evidence. In some cases, definitive diagnosis requires histopathological examination of tissue obtained via biopsy or resective epilepsy surgery.

Treatment

Treatment is directed at the underlying etiology, not the radiological sign itself. For Creutzfeldt-Jakob disease, care is supportive and may involve coordination with specialists in palliative medicine. If the finding is related to focal cortical dysplasia causing epilepsy, treatment involves antiseizure medications and evaluation for surgical resection at a comprehensive epilepsy center. Cases linked to autoimmune encephalitis are treated with immunomodulatory therapies such as corticosteroids, IVIG, or rituximab. Management is always multidisciplinary, involving neurologists, neuroradiologists, neurosurgeons, and neuropathologists.

Prognosis

The prognosis is entirely dependent on the causative condition. When associated with sporadic Creutzfeldt-Jakob disease, the prognosis is invariably poor, with rapid progression and fatality typically within a year. In contrast, when related to surgically amenable focal cortical dysplasia, complete seizure freedom can be achieved after resection, significantly improving quality of life. For autoimmune causes, early and aggressive treatment can lead to substantial recovery, though some patients may have residual cognitive deficits or epilepsy. Long-term follow-up with a neurology team is essential to monitor for disease progression or recurrence. Category:Medical signs Category:Neurology Category:Neuroradiology