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  • Pituitary Apoplexy: A Syndrome of Acute Visual Dysfunction

    Neuro-Ophthalmology/Orbit
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    Pituitary apoplexy is characterized by sudden onset of headache, visual symptoms, altered mental status, and hormonal dysfunction. It may be hemorrhagic or nonhemorrhagic. It may involve a pre-existing pituitary adenoma or a nonadenomatous gland, as in Sheehan syndrome, which is precipitated by postpartum uterine hemorrhage.1

    General Presentation of Pituitary Apoplexy

    Pituitary apoplexy syndrome stems from an acute expansion of a pituitary adenoma or, less commonly, in a nonadenomatous gland, from infarction or hemorrhage.2 Histologically, many of these tumors display hemorrhagic necrosis. Some researchers believe that apoplexy is more prevalent in patients who produce excessive amounts of pituitary hormones, as in acromegaly or Cushing syndrome, perhaps because tumor growth is fueled by these hormones.3 However, others report that most pituitary tumors that undergo apoplexy are endocrinologically silent.4 Reported predisposing factors include routine anterior pituitary stimulation tests, bromocriptine treatment, head trauma, surgery, pregnancy, and pituitary irradiation.5

    The clinical presentation of pituitary apoplexy is marked by severe headache in 95% of cases. The headache is sudden in onset; it results from the stretching of the dura mater in the walls of the sella supplied by the meningeal branches of cranial nerve V, the trigeminal nerve, and irritation of the trigeminal nerve itself by the expanding mass.

    Ocular paresis from pituitary apoplexy results from involvement of the cavernous sinus, making cranial nerves III, IV, and VI vulnerable to compression.4 The classic visual field defect is a bitemporal superior quadrantic defect from compression of the optic chiasm from below; however, field defects will show more diffuse loss with greater chiasmal fiber damage. The clinical manifestation of pituitary apoplexy may vary however, ranging from sudden headache in isolation, to headache associated with ophthalmoparesis or bitemporal visual field defects. The patient may even present with bilateral total blindness.

    Sheehan syndrome refers to pituitary apoplexy of a nontumerous gland precipitated by postpartum uterine blood loss with subsequent spasm of the arterioles supplying the anterior pituitary gland (adenohypophysis).6 In 1937, Sheehan reported on 11 patients who died in the puerperium, all of whom had necrosis of adenohypophysis. Nine of the patients had severe uterine hemorrhage at delivery. The other two patients had no hemorrhage but were gravely ill prior to delivery.6 A retained placenta may be associated with blood loss and hypovolemic shock. Normally, after the placenta is delivered, the uterus contracts and uterine bleeding halts. If the placenta is retained, the uterus cannot contract properly, so blood vessels will continue to bleed. Sheehan syndrome occurs in 1% to 2 % of women suffering significant postpartum uterine hemorrhage. Normally, the pituitary gland hypertrophies in pregnancy. This hypertrophy, combined with locally released factors, mediates vascular spasm and renders the pituitary more susceptible to infarction from compromised blood flow.

    Diagnosis and Treatment of Pituitary Apoplexy

    A characteristic magnetic resonance imaging (MRI) finding in pituitary apoplexy is an enlarged pituitary gland bulging under the optic chiasm with peripheral enhancement surrounding a hypointense gland.1 The presumed etiology of the hypointense center in the pituitary gland is necrosis. Vaphiades coined the phrase "pituitary ring sign" to denote this MRI appearance. He retrospectively reviewed the cranial MRI scans of patients with pituitary apoplexy; all displayed the pituitary ring sign (Figures 1,2). 7 The MRI differential diagnosis of the pituitary ring sign is lymphocytic hypophysitis, pituitary abscess and pituitary adenoma that has not undergone apoplexy.8 Lymphocytic hypophysitis is a rare inflammatory disorder of the pituitary gland commonly manifesting late in pregnancy or during the postpartum period. It can mimic pituitary adenoma. In the majority of cases, the diagnosis is made after pituitary surgery for suspected pituitary adenoma.9 Pituitary abscess is a rare life-threatening disease which has a similar presentation to large nonfunctioning adenomas. Lymphocytic hypophysitis, pituitary abscess, and pituitary adenoma all present different clinically than pituitary apoplexy.9 The main clinical differential diagnosis of pituitary apoplexy is subarachnoid hemorrhage with aneurysmal rupture, which displays different neuroimaging characteristics.

    Reprinted by permission of the Taylor & Francis Ltd. Neuro-Opthalmology, The “Pituitary Ring Sign”: An MRI Sign of Pituitary Apoplexy, Michael S. Vaphiades, 31:4, Jan 8, 2007, pages 111 – 116,
    Figure 1. T1-weighted coronal gadolinium-enhanced cranial MRI showing an enlarged pituitary compressing the optic chiasm.

    Reprinted by permission of the Taylor & Francis Ltd. Neuro-Opthalmology, The “Pituitary Ring Sign”: An MRI Sign of Pituitary Apoplexy, Michael S. Vaphiades, 31:4, Jan 8, 2007, pages 111 – 116,
    Figure 2. T1-weighted coronal gadolinium-enhanced cranial MRI.

    Treatment consists of medically stabilizing the patient (usually in the ICU), administering high-dose corticosteroids (most patients have hypopituitarism), evaluation of electrolytes, glucose, and administration of appropriate endocrinologic replacement therapy alone or combined with transsphenoidal surgical decompression of the tumor. 10,11

    Pituitary apoplexy is an important entity for general ophthalmologists to be familiar with because patients with this condition may initially present visual dysfunction. If the diagnosis of apoplexy is not made quickly and the patient treated emergently, there may be major complications including acute panhypopituitarism, permanent visual acuity or field loss and even death.

    References

    1. Vaphiades MS, Simmons D, Archer RL, Stringer W. Sheehan syndrome: a splinter of the mind. Surv Ophthalmol. 2003;48:230-233.
    2. Bills DC, Meyer FB, Laws ER Jr, et al. A retrospective analysis of pituitary apoplexy. Neurosurgery. 1993;33:602-609.
    3. Rovit RL, Fein JM. Pituitary Apoplexy: a Review and Reappraisal. J Neurosurg. 1972;37:280-288.
    4. Reid RL, Quigley ME, Yen SS. Pituitary apoplexy, a review. Arch Neurol. 1985;42:712-719.
    5. Biousse V, Newman NJ, Oyesiku NM. Precipitating factors in pituitary apoplexy. J Neurol Neurosurg Psychiatry. 2001;71:542-545.
    6. Sheehan HL. Post-partum necrosis of the anterior pituitary. J Pathol Bacteriol. 1937;45:189-214.
    7. Vaphiades MS. The "pituitary ring sign": An MRI sign of pituitary apoplexy. Neuro-Ophthalmology. 2007;31:111-116.
    8. Arita K, Tominaga A, Sugiyama K, et al. Natural course of incidentally found nonfunctioning pituitary adenoma, with special reference to pituitary apoplexy during follow-up examination. J Neurosurg. 2006;104:884-891.
    9. Flanagan DE, Ibrahim AE, Ellison DW, Armitage M, Gawne-Cain M, Lees PD. Inflammatory hypophysitis - the spectrum of disease. Acta Neurochir (Wien). 2002;144:47-56.
    10. Gruber A, Clayton J, Kumar S, Robertson I, Howlett TA, Mansell P. Pituitary apoplexy: retrospective review of 30 patients--is surgical intervention always necessary? Br J Neurosurg. 2006;20:379-385.
    11. Krisht AF, Vaphiades M, Husain M. Pituitary apoplexy, in Krisht AF, Tindall GT (ed): Pituitary Disorders, comprehensive management. Lippincott Williams & Wilkins, 1999, pp 295-303.

    Author Disclosure

    This work was supported in part by an unrestricted grant from Research to Prevent Blindness.

    Dr. Vaphiades states that he has no financial relationship with the manufacturer or provider of any product or service discussed in this article or with the manufacturer or provider of any competing product or service.