Non-Parenchymal vs. Parenchymal Involvement in Neuro-Behçet's Disease
In neuro-Behçet's disease, "non-parenchymal" refers to neurological involvement that affects the cerebral vessels rather than the brain tissue itself, primarily manifesting as cerebral venous sinus thrombosis, while "parenchymal" involvement affects the actual brain tissue, commonly in the brainstem and diencephalic regions.
Types of Neurological Involvement in Behçet's Disease
- Central nervous system involvement in Behçet's disease is classified into two major categories: parenchymal and non-parenchymal 1
- Parenchymal involvement is more common, occurring in approximately 61% of neuro-Behçet's cases, and affects the brain tissue itself, particularly the brainstem-diencephalic regions 2
- Non-parenchymal involvement occurs in about 28.6% of cases and primarily manifests as cerebral venous sinus thrombosis (CVST) 2
- A small percentage (6.5%) may have mixed involvement with both parenchymal and non-parenchymal features 2
Characteristics of Parenchymal Involvement
- Parenchymal neuro-Behçet's disease typically affects the brainstem (72.9% of cases), cerebellum (43.8%), and diencephalon (37.5%) 2
- Spinal cord involvement is less common, occurring in about 24.5% of parenchymal cases 2
- MRI findings in acute parenchymal neuro-Behçet's typically show mesodiencephalic lesions with a characteristic "cascade sign" (extension pattern from thalamus to midbrain) 1
- Cerebrospinal fluid (CSF) in parenchymal involvement generally shows pleocytosis and increased protein with normal glucose levels 1
- Parenchymal involvement can present as brainstem syndrome, multiple sclerosis-like presentations, movement disorders, or myelopathic syndrome 1
Characteristics of Non-Parenchymal Involvement
- Non-parenchymal involvement primarily manifests as cerebral venous sinus thrombosis (CVST) 1
- In contrast to parenchymal involvement, CSF in non-parenchymal cases typically shows increased pressure but normal cell count and composition 1
- Diagnosis of non-parenchymal involvement relies on brain MRI (particularly susceptibility-weighted images), MR venography, or CT venography 1
- Non-parenchymal neuro-Behçet's has a significantly better prognosis than parenchymal involvement 3
Treatment Differences
- For parenchymal involvement, high-dose glucocorticoids should be started together with immunosuppressives such as azathioprine 4
- Treatment for non-parenchymal involvement (cerebral venous thrombosis) consists of high-dose glucocorticoids followed by tapering, with anticoagulants potentially added for a short duration 4
- Cyclosporine-A should be avoided in patients with central nervous system involvement due to potential neurotoxicity 4
- For severe or refractory parenchymal disease, monoclonal anti-TNF antibodies should be considered 4
Clinical Significance and Prognosis
- The distinction between parenchymal and non-parenchymal involvement is important as they have different treatment approaches and prognoses 3
- Mortality is higher in parenchymal neuro-Behçet's disease compared to non-parenchymal involvement 2
- Approximately 58% of patients with acute onset parenchymal disease experience only one attack 2
- Eye involvement is more frequent in patients with parenchymal neuro-Behçet's disease compared to those with non-parenchymal involvement 2
Monitoring and Follow-up
- Regular assessment of inflammatory markers and neurological status is essential for patients with either form of neuro-Behçet's disease 5
- Patients with a history of parenchymal involvement require closer monitoring due to the potential for relapsing or progressive course 5
- Screening for vascular disease at extracranial sites is needed for patients diagnosed with cerebral venous thrombosis 6