Melanotroph pituitary adenoma in a cat with diabetes mellitus

Contains fulltext : 32729.pdf (publisher's version ) (Closed access)A 13-year-old male, castrated, crossbred cat was referred for insulin-resistant diabetes mellitus. The cat had a ravenous appetite and a dull coat. Basal urinary corticoid/creatinine ratios were normal. In the low-dose dexamethasone suppression test there was no suppression of the (nonelevated) plasma cortisol concentration, whereas the (nonelevated) plasma adrenocorticotropic hormone (ACTH) concentration declined to low values. Basal plasma alpha-melanocyte-stimulating hormone (alpha-MSH) concentrations were highly elevated (> 1,500 ng/liter). Computed tomography revealed a pituitary tumor originating from the pars intermedia (PI). After microsurgical transsphenoidal hypophysectomy, the clinical signs resolved and the cat no longer required insulin administration. Microscopic examination of the surgical specimen revealed a pituitary adenoma originating from the PI with infiltration into the neural lobe. The adenoma immunostained intensely positive for alpha-MSH and only weakly for ACTH. It is concluded that the ACTH-independent cortisol production was probably due to the (weak) glucocorticorticotropic effects of the extremely high plasma concentration of alpha-MSH and related peptides

CAVERNOUS HEMANGIOMA OF THE MESENCEPHALON: TONSILLOUVEAL TRANSAQUEDUCTAL APPROACH

OBJECTIVE: Recent advances in microsurgical techniques facilitate surgical resection of brainstem lesions that were previously considered inoperable. In this article we present, for the first time, the tonsillouveal transaqueductal approach to access a progressively symptomatic cavernoma within the depth of the tegmentum of the mesencephalon. METHODS: A 52-year-old woman presented with a history of slowly progressive right-sided hemiparesis and ataxia. On magnetic resonance imaging, a relatively large cavernoma involving the tegmentum of the mesencephalon was shown. The sylvian aqueduct was patent and there was no secondary ventriculomegaly. The patient underwent surgery via a suboccipital craniotomy and C1 laminectomy. The right tonsillouveal and medullotonsillar spaces were opened to the level of the choroidal point of the posteroinferior cerebellar artery. The tela choroidea was incised from the foramen of Magendie to the telovelar junction. Looking through the aqueduct and at a point 5 mm superior to its inferior inlet, there was a small cherry-like blister protruding into the aqueductal anterior surface. This was used as an entry point to access the cavernoma. The space around the cavernoma was gently dissected and the cavernoma was circumferentially coagulated to shrink it in a concentric manner toward its center. RESULTS: The total removal of the lesion was achieved and the histopathological findings were consistent with a cavernoma. As a result of noncommunicating hydrocephalus, the patient needed a ventriculoperitoneal shunt. The 1-year postoperative neurological examination was consistent with preoperative findings. CONCLUSION:This report shows, for the first time, direct surgical removal of a cavernous hemangioma in the mesencephalic tegmenturn via the aqueduct. This approach adds to contemporary microneurosurgery, respecting functional anatomy and minimizing neurological deficits