The story began two to three years before the young woman finally sought care. She experienced intermittent abdominal discomfort, recurrent vomiting, and mild to moderate headaches, symptoms that on their own could point in almost any direction in medicine. Then, over the final two to three months before presentation, her vision began to deteriorate in both eyes, progressively and relentlessly. Five days before she reached the outpatient department, she lost her sight entirely. By the time she was examined, she could perceive only fluctuating light in each eye. Her pupils remained equal and reactive to light, her mental functions were intact, and her limb strength was normal, but she showed subtle cerebellar signs on her left side, including an impaired finger-to-nose test and difficulty with rapid alternating movements.

Brain imaging explained much of what her examination could not. Computed tomography and magnetic resonance imaging revealed extensive, bilateral calcifications deposited in the basal ganglia, the thalami, and the dentate nuclei of the cerebellum, a distribution classic for Fahr-type intracranial calcification. Alongside these mineral deposits sat a well-defined cystic mass in the left cerebellum, with imaging features compatible with a pilocytic astrocytoma. Critically, the mass was compressing the fourth ventricle, the narrow channel through which cerebrospinal fluid drains from the brain’s interior, and the ventricles above it had dilated in response. The diagnosis was obstructive hydrocephalus, a build-up of fluid under pressure that, left untreated, is a neurosurgical emergency.

Fahr’s disease, more precisely termed primary familial brain calcification when no secondary cause can be identified, is a rare neurological disorder that most often affects young to middle-aged adults. The terminology matters: Fahr disease or PFBC refers to primary calcification without an identifiable underlying cause, while Fahr syndrome describes calcification arising secondary to another disorder, most commonly hypoparathyroidism or pseudohypoparathyroidism. In affected brains, abnormal deposits of calcium carbonate and calcium phosphate accumulate in the basal ganglia, thalamus, hippocampus, cerebral cortex, cerebellar white matter, and dentate nuclei. Clinically, these deposits are associated with movement disorders, psychiatric symptoms, cognitive impairment, and seizures. The pathogenesis is linked to disturbances in calcium metabolism and the neurovascular unit, and pathogenic variants in genes including SLC20A2, PDGFB, PDGFRB, XPR1, MYORG, and JAM2 have been implicated, several of which disrupt inorganic phosphate handling and the integrity of the blood-brain barrier.

Pilocytic astrocytoma is an entirely different entity. It is a World Health Organization Grade I glioma, a slow-growing and generally benign tumor that primarily strikes children and young adults, with a strong preference for the cerebellum. When completely resected, its prognosis is favorable. Its danger lies in location rather than biology: a cerebellar pilocytic astrocytoma can compress the fourth ventricle or the aqueduct of Sylvius, blocking cerebrospinal fluid outflow and driving intracranial pressure upward, producing exactly the progressive neurological decline this patient experienced. The coexistence of this tumor with Fahr-type calcification is extraordinarily rare, and it creates a diagnostic trap, because dense calcification can complicate radiological interpretation of posterior fossa lesions while the tumor-induced hydrocephalus demands urgent intervention.

Surgical treatment proceeded along standard lines for a posterior fossa mass with obstructive hydrocephalus. The neurosurgical team performed a suboccipital craniectomy and achieved gross total excision of the left cerebellar mass on operative assessment. When hydrocephalus persisted after the tumor was removed, the team placed a ventriculoperitoneal shunt, a catheter system that diverts excess cerebrospinal fluid from the ventricles to the abdominal cavity, a standard indication following posterior fossa tumor resection when fluid drainage fails to recover on its own. The postoperative course was uneventful. Headaches and vomiting gradually improved, and postoperative imaging showed expected surgical changes with the ventricular catheter correctly positioned. Vision, however, remained profoundly impaired.

Histopathology added an important layer of uncertainty. The resected tissue showed extensive hyalinization and regressive changes, with largely acellular material and no visible cellular areas, leading the pathologists to list pilocytic astrocytoma only as a possible differential diagnosis. This matters because regressive and degenerative features, including vascular hyalinization, calcification, and paucicellular fibrillary areas, are well recognized in pilocytic astrocytoma and can dominate the histological picture in long-standing lesions. Definitive confirmation would require the tumor’s characteristic bipolar piloid cells, Rosenthal fibers, and eosinophilic granular bodies, supported by GFAP immunohistochemistry and, where feasible, testing for the KIAA1549-BRAF fusion, which is present in approximately 90 percent of cerebellar pilocytic astrocytomas. Neither immunohistochemistry nor molecular testing was available in this case, so the tumor diagnosis remains presumptive.

The authors of the report are candid about the limits of what can be concluded. Serum calcium, phosphate, and parathyroid hormone levels were never obtained, so calcification secondary to a disorder of calcium metabolism could not be excluded biochemically, and the case cannot be firmly classified as primary familial brain calcification rather than Fahr syndrome. No family history was documented and no genetic testing was performed, leaving the calcification designation radiological rather than molecularly confirmed. Formal ophthalmologic assessment, including fundoscopy, grading of papilledema, and visual-field testing, was also unavailable, meaning the mechanism of visual loss must be inferred rather than directly demonstrated. Long-term follow-up is not yet established, and the team plans continued surveillance for visual recovery, tumor recurrence, and progression of the calcification.

The visual outcome deserves particular attention, because it carries the case’s most important clinical lesson. Posterior fossa masses rarely involve the visual pathway directly; bilateral visual failure most likely reflects raised intracranial pressure transmitted to the optic nerve heads, where sustained papilledema can produce axoplasmic stasis, ganglion cell axonal loss, and ultimately optic atrophy. Papilledema usually resolves after tumor resection or cerebrospinal fluid diversion, but deficits that are severe or long-standing at presentation may persist despite adequate treatment of the hydrocephalus, which accounts for the limited recovery observed here. Permanent visual loss is uncommon in posterior fossa tumors overall, reported in roughly 6 to 8 percent of children, and outcomes are generally most favorable for pilocytic astrocytoma, making the profound and largely irreversible deficit in this patient an atypical result. The authors argue it underscores the importance of early fundoscopic assessment and expedited cerebrospinal fluid diversion whenever visual symptoms accompany a posterior fossa mass.

How rare is this combination, really? A small number of comparable cases have been described. The first association was reported in 1984, when a patient’s scans showed Fahr-type calcification adjacent to a cystic astrocytoma. An autopsy study in 1993 identified a low-grade astrocytoma with extensive bilateral calcification and noted astrocytic proliferation near calcified deposits. In 2015, a 32-year-old woman was reported with bilateral calcification and an adjacent low-grade cystic astrocytoma, and the authors of that report observed a recurring pattern: relatively young patients with predominantly cerebellar tumors, where a cystic glioma arises next to a calcified dentate nucleus. In 2023, a coexistent meningioma broadened the reported tumor spectrum beyond astrocytoma. Current evidence suggests no established causal relationship between primary familial brain calcification and tumor development, and coexistence has generally been attributed to long-standing reactive astroglial proliferation around calcified deposits rather than a proven mechanism. Because the literature search underpinning this report was not systematic, the authors decline to assign a precise total to previously reported cases, and observations from a single patient cannot establish causation. What the case does establish is a diagnostic principle: when symptoms are progressive and disproportionate to any single diagnosis, clinicians should consider that more than one pathology may be at work, and they should match the certainty of their diagnostic language to the evidence actually available.

Subject of Research: Coexistence of Fahr-type intracranial calcification and a presumed cerebellar pilocytic astrocytoma with obstructive hydrocephalus

Article Title: Coexistence of Fahr‐Type Intracranial Calcification and a Presumed Cerebellar Pilocytic Astrocytoma With Obstructive Hydrocephalus: A Rare Case Report

Article References: Coexistence of Fahr‐Type Intracranial Calcification and a Presumed Cerebellar Pilocytic Astrocytoma With Obstructive Hydrocephalus: A Rare Case Report. (n.d.). https://doi.org/10.1002/ccr3.73552

Image Credits: AI Generated

DOI: 10.1002/ccr3.73552

Keywords: Fahr disease, primary familial brain calcification, pilocytic astrocytoma, obstructive hydrocephalus, cerebellar tumor, intracranial calcification, ventriculoperitoneal shunt, papilledema, posterior fossa, neurosurgery, SLC20A2, case report