Contribution of CT scan to the diagnosis of Fahr's syndrome.

Of 7040 patients who were examined with CT scan for various reasons, 72 (1.02%) showed symmetrical intracranial calcifications. On the basis of the extent of the calcifications, the patients were divided into 3 groups of which the first (10 cases), with extensive calcifications, showed clear findings of hypoparathyroidism; the second (4 cases), with less extensive calcifications, showed borderline laboratory findings and the third (58 cases), with calcifications only in the internal part of the globus pallidus, had no relation to any disturbance of the parathyroid function. The limited percentage (4.2%) of calcifications detected by ordinary cranial X-rays was discussed as compared to those diagnosed by CT scan; this is due to the weakening of the relationship which existed in the past between hypoparathyroidism and calcifications. Patients with extensive calcifications do not seem to have a significantly higher proportion of neurological impairment (35.8%) than patients who showed limited calcifications (34.5%). On the other hand, patients with extensive calcifications showed more frequent mental disorders (50%) compared to those who showed limited calcifications (34.5%). The proportion of mental disorders is still higher in patients with dilatation of the subarachnoid spaces (56.7%) compared to those who do not show dilatation (23.8%). Finally, of the 72 patients with calcifications, 15 (20.8%) showed extrapyramidal syndrome, possibly due to calcium salt deposits in the metasynaptic dopamine receptors while 13 (18%) were taking anticonvulsant drugs which, apart from influencing the metabolism of calcium, also influence the activity of alkaline phosphatase and are involved in the creation of calcifications.