Compressive optic neuropathy in fungal hypertrophic cranial pachymeningitis

Sir,

We report a rare case of compressive optic neuropathy secondary to hypertrophic cranial pachymeningitis. Fungal aetiology is rarely reported in the literature and can be life threatening.

Case report

A 73-year-old male presented with a 3-week history of left-sided visual loss, associated with headache, scalp tenderness, shoulder pain, and general fatigue. Of note in his medical history was type II diabetes mellitus and pulmonary asbestosis. There was no history of immunocompromise. On examination, his visual acuity was R 6/18 and L NPL, with a left afferent pupillary defect and left optic disc pallor, but a normal appearance of the right optic disc. The vision in his right eye was known to be reduced secondary to diabetic macular ischaemia. Neurological examination was otherwise unremarkable, as was his right visual field on Goldmann perimetry.

Initial blood tests revealed a white cell count of 12.7, ESR 61, and CRP 48. Temporal arteritis was initially suspected, but was ruled out with a negative temporal artery biopsy and lack of response to corticosteroid treatment.

MRI scanning showed an opacified left frontal sinus and large meningeal deposits with abnormal dural thickening and enhancement with gadolinium over both the sphenoid wings. There was compression of the left optic nerve at the anterior clinoid (see Figure 1). Lumbar puncture showed raised protein (567 mg/dl) without inflammatory cells. His left frontal sinus was drained, and culture grew Aspergillus flavus. A meningeal biopsy established the diagnosis as hypertrophic cranial pachymeningitis (HCP) caused by this organism. It was felt that the origin of his systemic fungal infection was pulmonary, as asbestosis is known to predispose to Aspergillus infection. He was commenced on systemic antifungal treatment, but his general medical condition rapidly deteriorated. He died 3 months later, secondary to respiratory failure and secondary overwhelming bacterial septicaemia.

Figure 1

T1-weighted post-contrast MR image showing extensive thickening and enhancing dura over the left sphenoid wing (arrowed).

Comment

HCP is a rare disorder characterized by diffuse or focal thickening and inflammation of the dura, and leads to all three meningeal layers becoming fused by dense fibrotic membranes.¹ Although several inflammatory and infectious causal agents have been identified, many cases are idiopathic. Patients usually present with multiple progressive cranial neuropathies, and the optic nerves and orbital apex are occasionally involved.² Blindness in HCP may be caused by constriction of the optic nerve by inflammatory thickening in the optic canal³ or direct inflammatory cell invasion of the optic nerve.⁴

CSF analysis in HCP varies according to the aetiology, and may be normal even in infective cases.⁵ Gadolinium-enhanced MR imaging is essential for identifying meningeal inflammation and also for locating suitable biopsy sites.

Optic nerve involvement in HCP usually confers a poor visual prognosis. Infective fungal cases are not well reported in the literature, but there is a significant mortality risk, and early diagnosis and treatment may be life saving. One report has shown some visual improvement and thinning of gadolinium-enhanced lesions on MRI, after systemic antifungal treatment.⁶ In non-infectious cases, some improvement in visual acuity has been shown with high dose corticosteroid treatment.^{2, 7}