Background
Idiopathic hypertrophic spinal pachymeningitis (IHSP) is a rare, chronic inflammatory condition marked by hypertrophic inflammation of the dura mater. This condition can occur throughout the entire spine but is most frequently observed in the cervical and thoracic regions. IHSP typically manifests during the 6th and 7th decades of life and can present as solitary or multiple lesions. It is an extremely rare, chronic progressive disease with symptoms related to the compression of neural structures or vascular compromise. The aetiology of IHSP remains unclear in most cases, although several causative factors have been identified, including trauma, sarcoidosis, rheumatoid arthritis, syphilis, tuberculosis, fungal infection, and meningococcal meningitis [1,2].
Clinical Perspectives
IHSP typically manifests during the 6th and 7th decades of life and can present as solitary or multiple lesions. The disease progresses in three stages due to the progressive compression of neural structures or vascular compromise. The first stage is characterised by increasing radicular symptoms. The second stage involves muscle weakness and atrophy. In the third stage, paraplegia, loss of bladder and bowel control, and respiratory distress from intercostal and diaphragmatic denervation become evident [2–4].
Imaging Perspective
MRI is the modality of choice for diagnosing spinal hypertrophic pachymeningitis due to its superior soft tissue resolution. This condition is characterised by dense fibrosis of the dura, with the most active inflammation occurring along the periphery of the lesion [4–6].
IHSP appears as a dura-based, hypointense, sheet-like mass (relative to the spinal cord) on both T1- and T2-weighted images, extending across multiple vertebral levels. The hypointensity is attributed to dense fibrosis, sparse interstitial space, and a lack of free water. The active inflammatory peripheral zone manifests as a thin, hyperintense edge on T2-weighted images, with intense peripheral enhancement and central non-enhancement. A predominantly peripheral enhancement pattern on post-contrast MRI images is highly suggestive of IHSP [3–5].
On CT, the hypertrophic meninges appear as slightly increased in density, with moderate or dense homogeneous enhancement.
Hypertrophic pachymeningitis due to metastasis, lymphoma, tuberculosis or IgG4-related causes are more frequently seen in cranial regions. Idiopathic hypertrophic pachymeningitis often exhibits peripheral T2 hyperintensity with post-contrast enhancement (sandwich-like pattern), contrasting with the absence of these features in cases of metastasis or lymphoma.
Outcome
The primary goal of management is symptom control, primarily achieved through surgical decompression via laminectomy or laminoplasty. Decompressive surgery for symptomatic compressive lesions, along with corticosteroid therapy to address the inflammation, remains the cornerstone of treatment. Surgery not only provides immediate decompression of the spinal cord but also enables tissue diagnosis [3,5].
Take Home Message
Patients with radiating upper limb pain or numbness, long extramedullary mass with low T2 signal intensity and peripheral enhancement on MRI are highly suggestive of IHSP.
All patient data have been completely anonymised throughout the entire manuscript and related files.
