Pachymeningitis

Pachymeningitis is inflammation of the dura mater, the outer protective layer of the brain and spinal cord. It can be diffuse or focal and may lead to thickening of the dura, a condition sometimes called hypertrophic pachymeningitis. It is distinct from leptomeningitis, which affects the arachnoid and pia.

Causes are diverse. Infectious etiologies include bacterial, tuberculous, fungal, and treponemal infections. Noninfectious causes encompass autoimmune or inflammatory diseases such as IgG4-related disease, granulomatosis with polyangiitis, sarcoidosis, and rheumatoid arthritis, as well as idiopathic cases.

Symptoms depend on affected areas. The most common complaint is chronic headache. Cranial neuropathies may occur from meningeal compression, producing vision or facial deficits. Spinal involvement can cause myelopathy or radiculopathy. Seizures and hydrocephalus are less common.

Diagnosis relies on imaging and laboratory tests. MRI with gadolinium typically shows thickened dura with enhancement; CT may reveal bone changes in chronic cases. CSF analysis often shows elevated protein with mild pleocytosis; infectious workup is guided by suspected etiology. Dural biopsy may be needed to define cause.

Treatment targets the underlying cause and inflammation. Corticosteroids are commonly first-line and many patients improve; immunosuppressants may be added for autoimmune etiologies or steroid-refractory disease. Treat infectious causes with appropriate antimicrobials. Long-term follow-up is common because relapses occur.

Prognosis varies with cause and extent. Many inflammatory forms respond to therapy, but chronic disease can cause lasting neurological deficits.