Idiopathic Hypertrophic Spinal Pachymeningitis: A Rare Cause of Spinal Cord Compression
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.271262
Source of Support: None, Conflict of Interest: None
Diseases solely affecting the dura of the spinal cord are rare. Idiopathic hypertrophic spinal pachymeningitis (HSP) is one such progressive inflammatory fibrosing disease of the spinal cord. It was first described by Charcot and Joffroy in 1869. It describes chronic inflammation of the spinal dura. This inflammation results in the thickening and hypertrophy of the dura with compression of the spinal cord. There are various manifestations of this disease ranging from radicular pain to weakness of limbs,, depending upon the level of involvement of the spinal dura. We describe a case of idiopathic HSP with involvement of the spinal dura at the level of the cervicothoracic region resulting in weakness of both lower limbs.
A 29-year-old otherwise healthy female presented after falling on due to stairs at her home. After two weeks, she developed pain in the neck. This was followed by a gradual onset weakness of both lower limbs. There was no involvement of bowel or bladder. On examination she had a power of 4/5 in both her lower limbs. Deep tendon reflexes were exaggerated from elbow and downwards. There was sensory level at the level of third thoracic vertebra. A diagnosis of compressive myelopathy at the cervicothoracic level was made clinically. Magnetic resonance imaging (MRI) scan revealed a space occupying lesion in the level of the cervicothoracic region which was seen compressing the spinal cord. The lesion was hypointense on T1W and T2W images. A diagnosis of a subacute subdural hematoma was considered in the background of a recent fall at that time. A differential diagnosis of intradural extramedullary tumor was also kept provisional. The patient was managed with steroids after which the power in her lower limbs improved. She was discharged with a gradual course of tapering steroids.
After six months, she again presented with similar complaints as previously. A repeat imaging revealed that the space-occupying lesion in the cervicothoracic region was persisting with same dimensions. It was hypointense on both T1W and T2W images. Upon contrast study, there was a linear peripheral enhancement in the anterior aspect of the lesion [Figure 1]a, [Figure 1]b, [Figure 1]c. The lesion was thickest in the region of the C7–T1 region. There was a hyperintense signal within the cord on T2W images suggestive of myelomalacia. A diagnosis of HSP was suggested from the MRI. Screening of the neuroaxis was performed and was normal. She was investigated for HSP and tested for autoimmune disorders as well as chronic granulomatous infections. ANCA, IgG4, ACA, and VDRL were all found to be negative. Cerebrospinal fluid (CSF) tapping was done which showed increased protein (200 mg/dl), glucose 60 mg/dl, and cells mostly lymphocytes.
At surgery, a laminectomy of C7–T1 was done. The dura was found to be intensely thickened the lesion was incised in the midline and dissected to find the underlying spinal cord [Figure 2]a. It was not possible to find the underlying cord at C7–T1 with a reasonable 1 cm cut. At this point, the skin incision was extended from C2 to T3 vertebrae. Laminectomy was done from C3 to T3 and the lesion was incised in the midline at the superior-most point. The underlying dura was seen compressed at this region. The lesion was then slowly dissected from the underlying spinal cord from the cranial to caudal direction. During this, the cord was seen severely compressed at the region of C7–T1. The lesion was found to be adherent to the exiting roots of the spinal cord and it was excised near totally [Figure 2]b. An expansile duroplasty was done using the synthetic dura G-Patch (Surgiwear Inc.) since the cord was sufficiently decompressed. The cut ends of the laminae were replaced and anchored to the facets using miniplates and screws. After she woke up from anesthesia, we observed that the power of her lower limbs had deteriorated to Grade 3/5. She was started on methyl prednisolone and she regained power of her lower limbs to preoperative levels one week later. She was discharged with advice to continue prednisone 20 mg per day.
The histopathology of the report showed extensive sclerosis with patchy and diffuse areas of inflammatory infiltrates consisting of plasma cells, lymphocytes, and eosinophils [Figure 3]a and [Figure 3]b. A diagnosis of HSP was confirmed.
She was followed up on an outpatient basis during which power both her lower limbs improved considerably and she was able to walk without support. However, the pain in her neck and brisk reflexes persisted which may improve in the future.
HSP was described by Park as a disease characterized by (1) unknown etiology, (2) specific dural involvement, (3) unique radiological features i.e., diffuse thickening of dura with encasement of CNS, and 4) unique histologic features i.e., chronic granulomatous inflammation of the dura. It is an infrequent cause of myelopathy. Due to the advent of better imaging facilities, there has been a surge of reported cases of HSP in the recent literature. Before the MRI era, cases were largely suspected on myelogram and corroborated with histopathology. Our search on the popular medical search engine PubMed revealed 39 cases of idiopathic HSP (IHSP) [Table 1]. Although differences exist with regards to gender predilection of this disease our literature review suggests that this disease manifests equally among both males and females. The most commonly affected patients are in the fifth and seventh decades of life. HSP can be either primary or secondary. Primary or IHSP is a diagnosis of exclusion when other causes of HSP has been ruled out. The secondary form of this disease is frequently associated with various autoimmune disorders like Wegener's granulomatosis; IgG4 related, rheumatoid arthritis, neuro Behçet's;,,,,, infectious diseases like tuberculosis,, syphilis; chronic granulomatous diseases like sarcoidosis; and heavy chain diseases, etc., The most common location of spinal forms of this disease is cervical followed by thoracic region., There have been reports of combined spinal and cranial form of this disease.,,,, The cranial form of this disease is mostly located in the base of skull and posterior fossa and presents often as multiple cranial nerve palsies. The most commonly involved cranial nerve is the seventh cranial nerve.
In the spinal form of HSP there is progressive fibrosis and sclerosing hypertrophy of the dura. The dura is thickened and compresses the underlying spinal cord which over the time manifest as myelopathy. The average onset of the disease symptoms varies in individuals from few weeks to months. According to a nationwide survey in Japan, nearly 50% of affected persons have a subacute onset of disease and in the remaining, hypertrophic pachymeningitis exhibits an acute or chronic pattern. There have been many instances in the literature where the disease has been misdiagnosed for other lesions. The most common differential diagnosis considered were epidural abscess,,, epidural hematoma, epidural lymphoma,, subdural hematoma,, and intradural extramedullary tumor.,,, Our patient had a history of fall following which she developed pain in the neck associated with weakness of both lower limbs. The possibility of an epidural hematoma was strongly considered in our patient in the first instance. However, she improved with steroids during the first admission only to be readmitted with recurrence of the symptoms after six months. The second MRI showed the lesion of the same dimension and characteristics, which prompted us to seek for an alternate diagnosis.
Radiology of IHSP is vital to the diagnosis. The entire neuroaxis need to be screened as this disease can coexist in both brain and spine concomitantly. In the cranial form, the symptoms can precede the development of the disease by as long as 2 years. The most common finding in this form is thickening of the falx and tentorium. The characteristic imaging findings of IHSP have been described in the review by Olubajo et al. A typical lesion is hypointense on T1- as well as T2-weighted images. However, there have been reports of lesions being hyperintense or isointense on T1W images and hyperintense, on T2W images. Upon contrast administration, varied observations have been reported from homogenous, nodular to linear peripheral pattern of enhancement. Our patient had a linear peripheral enhancement in the anterior region of the lesion. This type of peripheral enhancement has been suggested to represent active inflammatory zone and the non-enhancing central part to be fibrosis. The linear pattern of enhancement has also been correlated to be associated with with a better prognosis than homogenous or nodular.
Surgery for IHSP is controversial. Surgical decompression has to be performed in a setting of spinal cord compression. Early surgery has been advocated by Mikawa et al. to minimize the damage to the spinal cord. There have been many instances of patients undergoing multiple surgeries for recurrent disease. The dura in IHSP is thickened and closely adherent to the exiting roots of the spinal cord. Most authors in the literature have limited their maneuvers from, simple biopsy of the lesion,,,,, to partial excision of the lesion.,,,,, Very few have attempted a total excision. Early surgery helps to diagnose early and halt the progression of the disease. In our case, during surgery the lesion was found to be very firm and severely compressing the dura. We split the lesion in the midline and excised it near totally and augmented the dural space with duroplasty. This would give adequate room for expansion of the cord.
Steroids are the mainstay in the management of IHSP. Nearly all cases in the literature have been treated with steroids in addition to biopsy/surgery. The management of recurrences of this disease after failure of steroid therapy or cases in which steroids could not be given due to systemic intolerance is debatable. The most commonly used drugs in this scenario are methotrexate,, cyclophosphamide, melphalan, and anti-tuberculous therapy.
The outcome of IHSP is variable among the reported literature. Mostly the lesions have remained stable with steroids and surgery, whereas others have had multiple relapses. The recurrence of the lesions is suggested due to the inflammation of the dura present before the surgery and not due to the residual lesion. Tsutsui et al., observed in their review the chronological events in IHSP and suggested that they have either sustained remissions or relapse with corticosteroid resistance or dependence. Increased levels of CSF protein and cells have also been correlated to the recurrence of the disease. Mikawa et al. suggested in their review that patients with IHSP can be divided into two groups according to the presence or absence of systemic inflammation. The patients in the group with systemic signs of inflammation fared worse than without.
IHSP is a rare cause of spinal cord compression. Polyradiculopathy with myelopathy should alert the physician about this possibility. Early surgery in the setting of compression should prevent further damage and enhance recovery. The predictive factors for long-term cure are yet to be ascertained in large cohorts. However, steroids can successfully control the symptoms up to certain extent.
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[Figure 1], [Figure 2], [Figure 3]