Online newspaper of professor Yasser Metwally

The author: Professor Yasser Metwally

http://yassermetwally.com

INTRODUCTION

October 31, 2009 — Pseudotumor is divided into acute, subacute, and chronic forms. These subcategories are based on the degree of inflammatory and fibrovascular response.

• Acute stage

In the acute form of the disease, there is a polymorphous infiltrate composed of mature lymphocytes, plasma cells, macrophages, eosinophils, and polymorphonuclear lymphocytes. Multinucleated foreign body giant cells secondary to fibrosis also have been described but are rare. The cellular infiltrate or orbital pseudotumor tends to be diffuse and multifocal. Occasionally vasculitis, affecting small arteries of the orbit, may be associated with idiopathic orbital pseudotumor.

• Subacute stage

In the subacute and chronic idiopathic orbital pseudotumor, there is formation of increasing amounts of fibrovascular stroma affecting muscles, fat, and glandular elements. This fibrotic response may eventually result in dense fibrosis with fixation of orbital structures. Lymphoid follicles with germinal centers may be interspersed, especially in the chronic phase.

Figure 1. Chronic inflammatory reaction involving the orbital fat , extraocular muscles, and lacrimal gland (Click to enlarge figure)

The acute inflammatory process may lead gradually into the fibrotic stage; however, some cases of nonspecific idiopathic orbital inflammation are primarily sclerotic in nature and may present and progress insidiously without passing through a prior acute inflammatory phase.

The lacrimal gland is the most frequent orbital structure involved in pseudotumor. There is usually diffuse enlargement of the lacrimal gland with preservation of the shape of the gland. The most marked expansion occurs in the anteroposterior diameter along the lateral orbital wall and lateral rectus muscle. There may be an associated inflammatory reaction in the periglandular tissue imparting poor definition to the margins of the gland. There is usually pain and tenderness on palpation and some inflammation of the adjacent globe. There are no specific density characteristics on CT or MR images to differentiate glandular enlargement from other causes (bacterial inflammation sarcoid, or lymphoproliferative disease). Prompt response to steroid treatment, in conjunction with the radiologic findings, support the diagnosis of pseudotumor. A biopsy is indicated in cases where such response is lacking.

Occasionally, a pseudotumor forms an orbital mass that, however, is most often ill- defined and heterogeneous in composition. Some of these pseudotumor masses may invade the extraorbital structures, including intracranial cavity. Pseudotumor infiltrations may extend along the optic nerve sheath from the globe to the optic canal causing diffuse enlargement of the optic nerve sheath complex. On contrast CT, there is enhancement of the sheath contrasting against the central low density nerve .Orbital apex pseudotumor may compress, obliterate, or displace the optic nerve . The optic nerve sheath is characterized by a lucent band representing cerebrospinal fluid (CSF) in the subarachnoid space. A subcategory of diffuse orbital inflammatory pseudotumor is sclerosing pseudotumor. This process may represent the endstage of a subacute pseudotumor or may arise in the orbit de novo. There is a diffuse increase in density of the orbital fat with obliteration of the optic nerve, muscles, and circumferential involvement of the globe.

• Chronic stage

There is complete fixation of the intraorbital structures with no motion of the globe. If the inflammatory process in the orbital apex extends to the cavernous sinus, the Tolosa-Hunt syndrome is evoked. In these cases, there is enlargement of the cavernous sinus on the involved side. On CT and MR imaging, there is diffuse enhancement following administration of contrast material . Associated with these findings may be narrowing of the intracavernous carotid artery. The Tolosa-Hunt syndrome is characterized clinically by the onset of ophthalmoplegia. Following administration of steroids, symptoms abate and there is resolution of the cavernous inflammation.

Involvement of the globe is not an uncommon finding in pseudotumor. On the CT and MR imaging studies, there is diffuse enlargement of the sclero-uveal coat, which cannot be separated into the individual layers such as retina, choroid, or sclera.The inflammatory process is usually located in Tenon’s space, a potential space between Tenon’s capsule and the sclera. There is usually enhancement of the sclera following contrast administration. There may be an associated inflammatory reaction in the uvea, which is composed of choroid, ciliary body, and iris. Not infrequently, there is an associated inflammatory infiltrate in the adjacent anterior orbital fat around the globe.

• Differential diagnosis of pseudotumour of the orbit
  • Bacterial infection
  • Orbital cellulitis
  • Functional infections
  • Rhino-orbital mucormycosis
  • Aspergillosis
  • Sarcoidosis
  • Sjogren’s syndrome
  • Wegener’s granulomatosis

References

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2. Bruyn GW, Ferrari M, de Beer FC: Migraine, Tolosa-Hunt syndrome and pleocytosis. Correlation or coincidence? Clin Neurol Neurosurg 1984; 86(1): 33-41.
3. Cohn DF, Carasso R, Streifler M: Painful ophthalmoplegia: the Tolosa-Hunt syndrome . Eur Neurol 1979; 18(6): 373-81.
4. Goto Y, Hosokawa S, Goto I: Abnormality in the cavernous sinus in three patients with Tolosa-Hunt syndrome: MRI and CT findings. J Neurol Neurosurg Psychiatry 1990 Mar; 53(3): 231-4.
5. Hunt WE: Tolosa-Hunt syndrome: one cause of painful ophthalmoplegia. J Neurosurg 1976 May; 44(5): 544-9.
6. Johnston JL: Parasellar syndromes. Curr Neurol Neurosci Rep 2002 Sep; 2(5): 423-31.
7. Kline LB: The Tolosa-Hunt syndrome. Surv Ophthalmol 1982 Sep-Oct; 27(2): 79-95.
8. Kline LB, Hoyt WF: The Tolosa-Hunt syndrome. J Neurol Neurosurg Psychiatry 2001 Nov; 71(5): 577-82.
9. Kwan ESK, Wolpert SM, Hedges TR III: Tolosa-Hunt revisited: Not necessarily a diagnosis of exclusion. Am J Radiol 1989; 71: 932.
10. Roca PD: Painful ophthalmoplegia: the Tolosa-Hunt syndrome. Ann Ophthalmol 1975 Jun; 7(6): 828-34.
11. Schutta HS: Diseases of the Dura Mater. In: Joynt R, Griggs R, eds. Clinical Neurology. Philadelphia, Pa: Lippincott, Williams & Wilkins; 1993: 34-44.
12. Smith JL, Taxdal DS: Painful ophthalmoplegia. The Tolosa-Hunt syndrome. Am J Ophthalmol 1966 Jun; 61(6): 1466-72.
13. Sondheimer FK, Knapp J: Angiographic findings in the Tolosa-Hunt syndrome: painful ophthalmoplegia. Radiology 1973 Jan; 106(1): 105-12.
14. Spector RH, Fiandaca MS: The "sinister" Tolosa-Hunt syndrome. Neurology 1986 Feb; 36(2): 198-203.
15. Troost BT: In: Miller NR, Newman NJ, eds. Walsh & Hoyt’s Clinical Neuro-Ophthalmology. Philadelphia, Pa: Williams & Wilkins Company; 1998: 1727-29.
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The author: Professor Yasser Metwally

http://yassermetwally.com

INTRODUCTION

October 30, 2009 — Pituitary apoplexy is a rare form of hemorrhage or infarction of the pituitary gland and may occur spontaneously or in association with pituitary adenoma, head trauma, or hypovolemic shock. Pregnant patients are at risk for pituitary apoplexy because of the enlargement of the pituitary gland in response to estrogen [1]. As a hypervascular gland, the pituitary is vulnerable to arterial pressure changes and prone to hemorrhage. In the classically described Sheehan’s syndrome, postpartum hypovolemic shock results in adenohypophyseal vessel vasospasm and pituitary necrosis. Although the exact incidence of Sheehan’s syndrome is unknown, it is estimated to be the most common cause of panhypopituitarism in women of childbearing age [1].

Pituitary apoplexy may present with headache, vomiting, bilateral visual field abnormalities, alteration of consciousness, and cranial neuropathies resulting from cavernous sinus involvement. In addition, acute adrenal insufficiency, hypothyroidism, hypogonadism, growth hormone deficiency, hypoprolactinemia, and fluid and electrolyte disturbances may occur. Neuroimaging is crucial for the correct diagnosis of pituitary apoplexy. A 1999 review of patients who had pituitary apoplexy revealed that standard head CT identified only 21% of pituitary hemorrhages, whereas MRI correctly identified 88% [2].

While most patients recover spontaneously, many may experience long-term endocrine complications. Supportive care is indicated for all patients, with attention to blood pressure and neurological observation. Indications for medical and surgical treatment of pituitary apoplexy are controversial. Some authors recommend immediate corticosteroid supplementation in all patients suspected of having pituitary apoplexy so as to treat potential corticosteroid insufficiency [2,3]. Other investigators believe cranial nerve palsies often improve over time and that surgery should be reserved for patients who do not show improvement with high dosages of corticosteroids [4].

However, corticosteroids are category C medications and the decision to administer high doses of corticosteroids should, therefore, depend on the clinical status, including that of the pregnancy. Since most cases of pituitary apoplexy occur near term or postpartum the issue of corticosteroid safety during pregnancy is often not relevant. Others argue that the clinical course of apoplexy is unpredictable and transsphenoidal decompression is a safe and beneficial procedure [2]. There is, however, only one report of transsphenoidal surgery for pituitary apoplexy in a pregnant patient [5,6].

Lecture 1. Neuroimaging of pituitary adenomas

References

1. Mestman JH. Endocrine diseases in pregnancy. In: Gabbe SG, Niebyl JR, Simpson JL editor. Obstetrics: normal and problem pregnancies. 4th edition. Philadelphia: Churchill Livingstone; 2002;.
2. Randeva HS, Schoebel J, Byrne J, Esiri M, Adams CB, Wass JA. Classical pituitary apoplexy: clinical features, management and outcome. Clin Endocrinol. 1999;51:181–188.
3. Sam S, Molitch M. Timing and special concerns regarding endocrine surgery during pregnancy. Endocrinol Metab Clin North Am. 2003;32:337–354.
4. Maccagnan P, Macedo CL, Kayath MJ, Nogueira RG, Abucham J. Conservative management of pituitary apoplexy: a prospective study. J Clin Endocrinol Metab. 1995;80:2190–2197.
5. Lunardi P, Rizzo A, Missori P, Fraiolo B. Pituitary apoplexy in an acromegalic woman operated on during pregnancy by transphenoidal approach. Int J Gynaecol Obstet. 1991;34:71–74.
6. Metwally, MYM: Textbook of neuroimaging, A CD-ROM publication, (Metwally, MYM editor) WEB-CD agency for electronic publication, version 10.4a October 2009 [Click to have a look at the home page]
7. Neuroimaging of pituitary adenomas [Full text in PDF format]
8. The neurology of pregnancy [Full text]