35 Emergencies and Acute Situations in Skull Base Surgery

The incidence is six in 100,000 people, occurring in 1 to 9% of surgically treated pituitary adenomas. It has a male predilection, and the average age at presentation is 47 years. There is a 10% risk of apoplexy in incidentally discovered macroadenomas.1

• Pituitary adenomas often show asymptomatic bleeding, which is detected during surgery, on pathology, or on magnetic resonance imaging (MRI); 14 to 25% of patients with a pituitary adenoma have asymptomatic bleeding.^2–5 Pituitary apoplexy, therefore, is a clinical and not a pathological diagnosis.

• Prolactinomas, which are also the most frequent functional pituitary adenomas, have the highest incidence of apoplexy. Macroadenomas with suprasellar extensions are also prone to apoplexy.⁴

• In pituitary tumors, apoplexy/ischemia may occur because of the rapid growth of the tumor.^3,6

• The risk of apoplexy is 0.6 to 10% in incidentally discovered macroadenomas.^5–10

• About 80% of patients who present with apoplexy have no prior pituitary tumor diagnosis.⁶

Pituitary apoplexy can also occur in the nonneoplastic pituitary gland (after postpartum hypotension, for example, in Sheehan’s syndrome) and rarely in other sellar lesions, such as tuberculosis, craniopharyngioma, and lymphocytic hypophysitis.^11–13

Apoplexy Progression

Progression occurs as follows: tumor expansion hemorrhage or infarct compression on the surrounding pituitary parenchyma partial destruction of the normal pituitary gland acute compression of surrounding structures potential extravasation of blood in the subarachnoid space.14

The increased intrasellar pressure, due to the acute expansion of the hematoma, may be the cause of ischemic necrosis following hypopituitarism.¹⁵

Risk Factors

Various precipitating factors have been implicated in pituitary apoplexy, such as hypertension,^16,17 dopamine agonists,¹⁸ antithrombotic therapy,^18,19 estrogen therapy, radiation therapy, major surgery, and head trauma.^3,17 Pregnancy has also been related to pituitary apoplexy^20,21 leading to Sheehan’s syndrome.

Pituitary stimulation tests with gonadotropin-releasing hormone, thyrotropin-releasing hormone, and corticotropin-releasing hormone may also induce pituitary apoplexy; thus, these patients should be closed monitored for apoplexy if they have been previously diagnosed with a pituitary tumor or if this diagnosis is suspected.¹⁷

Signs and Symptoms

There is atypical triad of symptoms: acute headache, visual deficits, and panhypopituitarism.

• Acute severe headache, often retro-orbital and sometimes occipital, has an onset and severity similar to that in subarachnoid hemorrhage. Headache is the most common symptom in pituitary apoplexy, occurring in 95% of cases, typically accompanied by nausea and vomiting (43–80% of cases), and less commonly by photophobia, fever, and decreased level of consciousness.¹ It may be mistaken for a subarachnoid hemorrhage or missed in the emergency department by clinicians or radiologists who fail to consider pituitary apoplexy in the differential diagnosis because pituitary apoplexy is less likely to cause meningeal signs.

• Visual field deficits are generally bitemporal superior quadrantanopsia or bitemporal hemianopsia. Decreased visual acuity occurs in 46 to 82% of patients,^{5,8,16,22–24} with a range of symptoms from blurry vision to blindness.

• Diplopia occurs in 40 to 69% of patients. It is generally due to cranial nerve (CN) III palsy (unilateral dilated pupil, ptosis, eyeball deviated inferolaterally). Less frequently due to CN IV or VI palsy.^8,16,22,25 Up to 40% of patients can have combined deficits, generally involving CNs III and VI together.^8,16,22

• Hypopituitarism: The most significant and life-threatening deficiency is secondary hypoadrenalism, although the most frequent is secondary hypogonadism. Diabetes insipidus occurs in fewer than 8% of cases of pituitary apoplexy.16

• Other possible signs include Horner’s syndrome, facial pain, and sensory loss due to trigeminal involvement (generally in CN V₁ or V₂).

• Rarely, pituitary apoplexy may lead to meningismus, stupor, and coma,²⁵ or neurologic symptoms related to vasospasm due to subarachnoid bleeding or internal carotid artery (ICA) compression.^5,26

Imaging

• Computed tomography (CT) scans show blood hyperdensity in the sella in cases of bleeding. Injection of contrast shows increased uptake in the residual pituitary parenchyma. CT scan detects pituitary apoplexy in fewer than 28% of cases.^16,17

• MRI is the best way to detect pituitary hemorrhage if apoplexy is suspected clinically.^16,17

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Hi-Tech Tools in Skull Base Surgery Craniovertebral Junction Functional Anatomy of the Cranial Nerves Skull Base Infections Skull Base Reconstruction Techniques Transcranial Approaches to the Skull Base

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