What are the outward signs of parenchymal involvement in neuro-Behçet's disease?

Outward Signs of Parenchymal Involvement in Neuro-Behçet's Disease

The most common outward signs of parenchymal involvement in neuro-Behçet's disease include brainstem syndrome with dysarthria, ataxia, hemiparesis, and cranial nerve palsies, which typically present as subacute neurological deficits. 1, 2

Clinical Manifestations of Parenchymal Involvement

• Parenchymal involvement is the most common form of neuro-Behçet's disease, occurring in approximately 60-70% of neurological cases 1, 3
• Brainstem syndrome is the predominant presentation, characterized by:
  • Dysarthria (slurred speech) 2
  • Ataxia (impaired coordination) 2
  • Hemiparesis (weakness affecting one side of the body) 1
  • Cranial nerve palsies (particularly affecting eye movements and facial muscles) 3
• Pseudobulbar syndrome may develop, presenting with:
  • Difficulty swallowing (dysphagia) 3
  • Emotional lability 3
  • Dysarthria 3
• Cerebellar signs are common, including:
  • Gait ataxia 3
  • Limb dysmetria 3
  • Nystagmus 3
• Movement disorders may occur, though less commonly:
  • Chorea has been reported in rare cases 3

Distinguishing Parenchymal from Non-Parenchymal Involvement

• Parenchymal involvement affects the brain tissue itself, while non-parenchymal involvement primarily affects blood vessels 1
• Non-parenchymal manifestations include:
  • Cerebral venous sinus thrombosis (CVST) presenting with headache, vomiting, and papilledema 3
  • Intracranial hypertension 3
  • Arterial involvement (rare) 3
• These two types rarely occur in the same individual and likely have different pathogenic mechanisms 4

Diagnostic Findings

• Cerebrospinal fluid (CSF) analysis in parenchymal neuro-Behçet's typically shows:
  • Pleocytosis (increased white blood cells) 1
  • Elevated protein levels 1
  • Normal glucose levels 1
• Brain MRI findings in acute parenchymal involvement include:
  • Mesodiencephalic lesions (characteristic) 1
  • "Cascade sign" - pattern of extension from thalamus to midbrain 1
  • Ill-defined areas of edema with high signal intensity on T2-FLAIR images 5
  • Lesions commonly affecting brainstem, basal ganglia, and thalamus 5
• Chronic parenchymal involvement may show:
  • Brain or brainstem atrophy 1
  • "Black holes" on MRI 1

Clinical Course and Prognosis

• Parenchymal involvement generally has a worse prognosis than non-parenchymal forms 3
• Mortality is higher in parenchymal involvement compared to non-parenchymal forms 3
• Neurological sequelae are common, with only about 54% of patients having a good outcome 3

Treatment Considerations

• For parenchymal involvement, the European League Against Rheumatism recommends:
  • High-dose corticosteroids for acute attacks 6, 7
  • Immunosuppressive agents including azathioprine, interferon-alpha, cyclophosphamide, methotrexate, and TNF-alpha antagonists 6, 7
• Cyclosporine A should be avoided in patients with central nervous system involvement due to potential neurotoxicity 6, 7

Important Clinical Pitfalls

• Neurological symptoms may be the initial presentation of Behçet's disease, making diagnosis challenging 5
• Parenchymal and non-parenchymal forms require different treatment approaches 1
• Young men with early disease onset have a higher risk of severe neurological involvement 7
• Regular monitoring with clinical assessment and inflammatory markers is essential 8