The most common symptom of pituitary apoplexy is headache. Almost all patients describe a sudden, severe retro-orbital or bifrontal headache, which is associated with vomiting in two thirds of cases. The headache and vomiting result from the sudden increase in intrasellar pressure either caused by the hemorrhage or secondary to meningeal irritation from blood or tumor products that leak into the CSF. The increase in intrasellar pressure results in many of the symptoms and signs of pituitary tumor apoplexy.
Laterally, the increased pressure causes compression of the structures in the cavernous sinus, namely the third, fourth, and sixth cranial nerves, with the third being most commonly affected as a result of its vulnerable position (parallel to the lateral wall of the pituitary gland). The sixth cranial nerve is the least commonly involved because of its most lateral location within the sinus. Ophthalmoplegia (caused by third, fourth, and sixth nerve palsies or any combination thereof) is present in around 80% of patients presenting with pituitary tumor apoplexy. The trigeminal nerve is also located within the cavernous sinus; its involvement may cause facial pain or sensory loss. Carotid siphon compression may present as hemiplegia. Superiorly, the increased pressure compresses the optic chiasm, optic tract, or optic nerve, leading to decreased visual acuity or visual field defects (classically, bitemporal hemianopsia). Blood leaking into the subarachnoid space may result in chemical meningitis with fever, meningismus, and photophobia. Fever in patients with apoplexy may also be explained by alteration in thermal regulation caused by hypothalamic involvement by the hemorrhage or by adrenal insufficiency associated with hypopituitarism. Hemorrhage may extend into the brain parenchyma causing cortical irritation and provoking seizures.
The elevated intrasellar pressure also accounts for the endocrine abnormalities found in cases of pituitary tumor apoplexy. This pressure increase results in compression of the pituitary tissue, compromising its vascular supply and leading to hypopituitarism. Adrenal insufficiency is the most clinically significant result of hypopituitarism, contributing significantly to the mortality of patients with pituitary tumor apoplexy if not promptly recognized and treated. Although not common, patients with pituitary tumor apoplexy may have diabetes insipidus at presentation. The true etiology of diabetes insipidus in this setting is unknown, but it may result from the increased pressure on the pituitary infundibulum, which impedes the antidiuretic hormone from passing from the hypothalamus to the posterior lobe of the pituitary.
A precipitating factor is identified in 50% of cases of pituitary tumor apoplexy. Predisposing factors include dopamine agonist treatment, head trauma, pituitary irradiation, pregnancy, coronary artery bypass grafting, surgical operations, and anticoagulation. Endocrine stimulation tests are also associated with pituitary tumor apoplexy. Hormones used in these tests may increase blood flow in pituitary adenomas, provoking bleeding in friable vessels. Pituitary tumor apoplexy following childbirth associated with significant postpartum hemorrhage in nontumorous glands is termed "Sheehan syndrome." The hypertrophy of the pituitary gland that occurs in normal pregnancy combined with the arterial spasm of the pituitary's blood supply (caused by bleeding and hypotension) both contribute to the development of Sheehan syndrome; however, the clinical presentation of pituitary apoplexy in these cases is usually less dramatic, with a more gradual development of signs and symptoms of hypopituitarism.
The diagnosis of pituitary tumor apoplexy is best established by MRI; however, this is usually preceded by a rapid diagnostic CT scan to screen for intracranial hemorrhage. MRI is superior to CT scanning for evaluating the pituitary gland and possibly visualizing hemorrhage not seen by CT. In one study, the detection rate of pituitary tumor apoplexy by CT scanning was 21%, whereas the detection rate was 100% with MRI.
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Cite this: Mousa Abujbara. Emergency Med Case Challenge: A 41-Year-Old on Sildenafil With a Headache While Sleeping - Medscape - Aug 22, 2022.