Anatomy and vascularization of the pituitary gland: a) The pituitary gland is located in the sphenoid bone (sella turcica) and is composed of the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The anterior lobe is composed of three parts: the pars distalis, which is the main component of adenohypophysis that secretes anterior pituitary hormones; the pars intermedia, which is suppressed in humans; and the pars tuberalis, which surrounds the infundibulum. The optic chiasma (where the optic nerves cross) is located on top of the superior part of the pituitary gland. b) The infundibulum, median eminence, pars tuberalis and posterior lobe are supplied by the internal carotid artery, whereas the pars distalis receives most of its blood supply from venous drainage from the infundibulum and the posterior lobe of the pituitary gland. The venous blood supply makes the anterior pituitary gland vulnerable to disturbances in blood supply. | Karaca, Z., Laway, B. A., Dokmetas, H. S., Atmaca, H., & Kelestimur, F. (2016). Sheehan syndrome, 2, 16092. Retrieved from http://dx.doi.org/10.1038/nrdp.2016.92
Hypothalamic-pituitary-adrenal axis:
Regulation of the hypothalamic–pituitary– adrenal axis: Glucocorticoid secretion is regulated by adrenocorticotropic hormone (ACTH) secretion from the pituitary gland, which is stimulated by corticotropin releasing hormone (CRH) secretion from the hypothalamus. CRH is suggested to be regulated from the upper centres of the brain. Glucocorticoids have negative-feedback effects on the upper centres of the brain, the hypothalamus and the pituitary gland. ACTH not only stimulates glucocorticoids but also stimulates adrenal androgens and mineralocorticoids. However, given that aldosterone secretion is primarily regulated by the renin– angiotensin system, ACTH deficiency does not result in mineralocorticoid deficiency, but leads to glucocorticoid deficiency and adrenal androgen deficiency in women. | Karaca, Z., Laway, B. A., Dokmetas, H. S., Atmaca, H., & Kelestimur, F. (2016). Sheehan syndrome, 2, 16092. Retrieved from http://dx.doi.org/10.1038/nrdp.2016.92
Pathology:
Mechanisms contributing to the clinical picture in pituitary apoplexy | Nawar RN, AbdelMannan D, Selman WR, Arafah BM. Pituitary tumor apoplexy: a review. J Intensive Care. 2008;23:75-90.
Presentation
Triad:
Thunderclap headache (> 90-97%): Sudden, severe head pain, frequently retro-orbital in location
Vomiting
Visual disturbances
Visual disturbances (#2 symptom, 50-82%):
Due to sudden haemorrhage-related increase in tumour mass, leading to compression of surrounding structures (mainly the optic chiasm or optic nerves, from upward expansion of the tumour).
Variable degrees of visual-field impairment:
Bitemporal hemianopsia (M/C visual disturbance)
Loss of visual acuity and blindness
Oculomotor palsies (52%):
Functional impairment of cranial nerves III, IV, and VI, due to intracavernous expansion of the tumour mass, a hematoma or, most frequently, to an abrupt pressure increase in the pituitary region (the cranial nerves are exquisitely sensitive to increased pressure)
CN III palsy: (M/C, half of cranial nerve palsies): Characterized by ptosis, limited eye movements in adduction, and mydriasis
Other neurological signs:
Due to extravasation of blood or necrotic tissue into the subarachnoid space.
Meningeal irritation:
Photophobia (40%)
Nausea, vomiting (57%)
Meningismus (25%)
Fever (16%), may be misleading.
Altered consciousness (ranging from lethargy to stupor or even coma)
Focal neurological deficits (hemiparesis or dysphasia, or to a pyramidal syndrome):
D/t Cerebral ischemia can occasionally result from mechanical compression of the carotid artery against the anterior clinoid, or to cerebral vasospasm
Less frequent neurological manifestations:
Anosmia (due to olfactory nerve compression)
Epistaxis/CSF rhinorrhea (due to erosion of the bone of the sella turcica)
Facial pain (due to compression of cranial nerve V)
Acute adrenal insufficiency (may lead to collapse and vital signs changes)
Endocrine dysfunction:
Corticotropic deficiency (M/C, 50–80%)
M/life-threatening hormonal complication, potentially causing severe hemodynamic problems and hyponatremia
Glucocorticoid deficiency →
Mineralocorticoid levels normal in ACTH-deficient patients (as it is mainly dependent on renin-angiotensin system)
Diabetes insipidus (rare, < 5%)
Diagnosis
CT scan:
Often the first imaging tool in PA, showing areas of hyperdensity within the sellar region.
CT appearance of pituitary apoplexy. Arrows on axial (a), coronal (b) and sagittal (c) reconstructions indicate an intrasellar lesion, dis-homogeneously hyperdense, due to the presence of haemorrhagic components. The utility of reformatted images in the evaluation of the intrasellar hyperdensity is evident | Boellis, A., di Napoli, A., Romano, A., & Bozzao, A. (2014). Pituitary apoplexy: an update on clinical and imaging features. Insights into imaging, 5(6), 753–762. doi:10.1007/s13244-014-0362-0
MRI:
Confirm haemorrhage within the pituitary gland and compression on the optic chiasm.
MRI performed in a patient with acute headache, mydriasis and visual impairment shows acute/early subacute phase haemorrhagic infarction within a pituitary macroadenoma. The intrasellar mass appears slightly hyperintense on unenhanced T1WI (axial, a; coronal, b; sagittal, c) with areas of hypointense signal on T2WI (axial, d; coronal, e) because of the presence of deoxyhaemoglobin. Coronal T1 contrast-enanched images (f) show left cavernous sinus involvement, probably leading to visual symptoms | Boellis, A., di Napoli, A., Romano, A., & Bozzao, A. (2014). Pituitary apoplexy: an update on clinical and imaging features. Insights into imaging, 5(6), 753–762. doi:10.1007/s13244-014-0362-0
Differential diagnosis:
Subarachnoid haemorrhage (can be distinguished from apoplexy by MRI with MR angiogram)
Infectious meningitis
Cavernous sinus thrombosis
Migraine
Rathke cyst haemorrhage
Hyperemesis gravidarum
Stroke
Management
Treatment of Pituitary Apoplexy | Hannoush ZC, Weiss RE. Pituitary Apoplexy. [Updated 2018 Apr 22]. In: Feingold KR, Anawalt B, Boyce A, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com, Inc.; 2000-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279125/
