Objective The objective of this case report is to emphasize the importance of considering uncommon conditions like Fahr’s disease in the differential diagnosis of seizures and cognitive impairment, especially in patients with a history of thyroidectomy. Material and Methods A 56-year-old woman who had undergone subtotal thyroidectomy 25 years previously presented with movement disorder and cognitive impairment secondary to hypoparathyroidism. A CT scan of the brain showed pathognomonic bilateral calcification in the basal ganglia, thalamus and cerebellar nuclei. Result The patient was diagnosed with Fahr’s disease caused by post-thyroidectomy hypoparathyroidism and successfully managed with oral calcium, carbidopa/levodopa and haloperidol. Conclusion We recommend the routine use of CT scanning in the long-term follow-up of post-thyroidectomy patients. LEARNING POINTS CT scans of the brain should be routinely carried out as part of long-term follow-up after thyroidectomy. Cognitive impairment and/or seizures should also be investigated using brain imaging. Taking a detailed history is a cornerstone of diagnosis in internal medicine.