Cranial pachymeningitis remains a poorly understood syndrome defined by meningeal thickening and typical gadolinium enhancement on magnetic resonance imaging (MRI). It is a rare disease with protean manifestations including many ophthalmological symptoms.

It can be caused by infections, neoplasia, or autoimmune disorders.[¹] Nevertheless, evaluation often fails to reveal a cause so it is supposed to be idiopathic.[²]

In December 2008, a 70-year-old man presented to our institution with blurred vision, floaters, and visual field shrinkage. His medical history included right eye evisceration in 1997 due to retinal detachment complications, hyperuricemia, arterial hypertension, open-angle glaucoma, and prostatic resection in December 2008. His usual treatments were carteolol eye drops, captopril–hydrochlorothiazide combination, amlodipine, acetylsalicylic acid, ketoprofene, and colchicine.

Being monocular, this man had always had careful ophthalmological follow-up and regular glaucoma assessments showing a stable normal visual field.

Ophthalmological examination in January 2009 showed a decreased visual acuity of 20/32 in the left eye, while it was 20/20 in November 2008. Slit-lamp examination, ocular motility, and fundus were normal. Pupillary examination showed a decreased myosis to light. Goldman visual field showed generalized constriction to 30 degrees [Figure 1a]. Brain MRI was performed in which a diffuse meningeal thickening with gadolinium enhancement was observed, suggesting the diagnosis of pachymeningitis [Figures 2–4]. Fortuitously, an aneurysm located in the anterior communicant artery and measuring 9 mm was discovered.

A complete clinical, biological, radiological, inflammatory, and infectious assessment was performed in March 2009. The complete blood count showed: 9.75 Giga. L-1 leucocytes, 2% lymphocytes being of a large hyperbasophil form. Sedimentation rate was 16 mm after an hour; C-reactive protein was 5.5 mg. L-1. Infectious assessment showed significant rates of anti-toxoplasmosis IgM and IgG antibodies which increased between two blood samples spaced out of a month. The infectious and inflammatory assessment including herpes viridae serology, TPHA-VDRL, Lyme disease serology, HIV test, quantiferon test, angiotensin converting enzyme, antineutrophil cytoplasmic antibodies, and antinuclear antibodies cyclic citrullinated peptide antibodies was normal.

Before the lumbar puncture, as the patient recently received peridural anesthesia for prostatic resection, a cerebrospinal MRI searching arguments for intracranial hypotension was performed, but it did not show any cerebrospinal leakage.

The lumbar puncture showed an increased protein level; chloride and glucose levels were normal. There were 24 red blood cells mm-3 and 10 leucocytes mm-3, but the cell analysis could not be performed because of the insufficient quantity of cerebrospinal fluid. Toxoplasmosis serology and PCR, cytology for carcinomatous cells in cerebrospinal fluid were normal. The opening pressure on lumbar puncture was normal at 13 cm H₂O. Serum and cerebrospinal fluid immune electrophoresis showed IgM and IgG antibody oligoclonal bands in both samples.

As seroconversion for toxoplasmosis was the only relevant result, oral trimethoprim-sulfamethoxazole combination 12 g/day was administrated during a month (April 2009), but the occurrence of a medicamentous hepatitis led to cessation of treatment 3 days earlier. The visual acuity increased to 20/25 in his left eye, but the Goldman visual field poorly improved and remained constricted. MRI brain imaging performed in May 2009 [Figure 5] showed the resolution of the pachymeningitis, but the optical coherence tomography imaging showed an atrophy of the optic disc in the left eye [Figure 6]. Aneurysm embolization was performed a few months later with no modification of the visual field.

Cranial pachymeningitis is a very rare disease with only a few cases described. Different etiologies are known: [Table 1] essentially rheumatoid polyarthritis,[³–⁵] sarcoidosis,[¹–⁶] tuberculosis,[⁷–⁹] intracranial hypotension,[¹⁰] and idiopathic pachymeningitis.[⁷]

Wegener granulomatosis[²] or systemic lupus erythematosus have also been described.[¹¹] Several authors report that Borrelia infections,[^{12, 13}] syphilis, or fungal infections can present with similar clinical and radiological features.[⁷] A case of Listeria has been described.[¹⁴] Pachymeningitis can be due to HIV: Either HIV virus or opportunist infections occurring in HIV.[^{15, 16}] It can be related to neoplasia too: Solid cancers or hemopathies.[¹⁷–¹⁹] A negative exhaustive assessment leads to diagnosis of idiopathic pachymeningitis.[⁷]

Isolated toxoplasmic pachymeningitis has never been reported except in case of congenital toxoplasmosis with generalized systemic locations.[²⁰]

By definition, an abnormal dural enhancement is detected on MRI.[²] Pachymeningeal thickening can be diffuse or localized.[⁷] The enhancement pattern can be nodular, linear, or both.[²] Thickening of the dura mater can involve cranial bones, pericranial soft tissue, and, rarely, the cerebral parenchyma.[⁷] Brain MRI shows iso- or hypointense thickened dura in T1-weighted images with characteristic gadolinium enhancement [Figure 2]. T2-weighted images can give informations about the inflammation severity and the prognosis: Indeed, classical T2-weighted images show a central hypointense area which represents the fibrous reacting tissue, while a peripheral hyperintense border represents the degree of inflammation.[^{7, 21, 22}]

In our patient, gadolinium enhancement surrounding the optic nerve gain in Fatsat T1-weighted images [Figure 3] confirms that visual loss and visual field shrinkage can be attributed to pachymeningitis. In T2-weighted images [Figure 4], the hyperintense peripheral area being important and inhomogeneous, it suggests an intense inflammation with risks of definitive visual damages.[⁷]

In Kupersmith et al., a series of 12 patients with idiopathic hypertrophic pachymeningitis, headache was the most frequent symptom, occurring in 92% of patients; unilateral or bilateral vision loss linked to optic neuropathy was the next most frequent symptom, occurring in 58% cases, from 20/30 to complete blindness. 66% had ophthalmoparesis, 13% had papilledema, and 13% presented ataxia.[²]

Multiple cranial nerve involvement can be explained by their compression at skull base by thickened pachymeninges.[²³] Neurological deficits may appear due to cortical irritation, mass effect of nodular pachymeningitis,[⁷] or compressive vessel occlusion by stenosis at the skull base,[²⁴] affecting either arteries or venous sinuses.[^{2, 7}] Rare cases of sudden death have been described in the literature.[^{25, 26}]

In our case, the absence of complete visual field resolution resulted from ischemia due to optic nerve compression which was objectified by evolution toward atrophy [Figure 6].

Assessment of pachymeningitis requires a clinical examination, blood and cerebrospinal fluid samples, chest X-ray or computed tomography, and brain MRI. When all results are negative or when symptoms worsen despite treatment, a meningeal biopsy can be performed.[²]

In this case, the toxoplasmic seroconversion was strongly suspected to be responsible for the pachymeningitis even if serologic tests and PCR were negative in cerebrospinal fluid: In patients with known toxoplasmic central nervous system lesions, only 28% show positive antibody in both serum and cerebrospinal fluid, this complex relationship can be explained by the blood-brain barrier,[²⁷] and PCR is rarely useful for diagnosis in immunocompetent patients.[²⁸]

The aneurysm could not be responsible for the condition: It classically leads to visual amputation more than constriction. Furthermore, the aneurysm embolization did not modify the visual field.

Hence treatment was initiated and another MRI was performed. Clinical improvement and favorable imaging evolution [Figure 5] favored the diagnosis of toxoplasmosis implication.

Even if it is a rare disease, ophthalmologists should think about pachymeningitis in case of unexplained visual loss or visual field shrinkage. A detailed assessment is needed to identify the etiology but idiopathic forms exist. Among the various infectious causes, toxoplasmosis must be screened for, because it can lead to pachymeningitis and its severe ultimate damages such as blindness, neurological deficits or even death.

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