October 16, 2015
4 min read

Hypophysitis and the ‘dural tail sign’

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A 34-year-old woman was referred for evaluation of a pituitary mass. The patient reported that she was well until her 38th week of her fifth pregnancy, when she developed blurred vision and 8 to 10 days of a frontal headache.

An MRI without contrast was performed that showed a sellar mass extending into the suprasellar cistern measuring approximately 1.7 cm x 1.2 cm x 2.1 cm (craniocaudal [CC] x anteroposterior [AP] x transverse [TV]). There was a mass effect on the optic chiasm, which was displaced superiorly. No evidence of pituitary hemorrhage or cystic degeneration was found.

The patient reported no nausea, vomiting, fatigue or dizziness. Her pregnancy had been uneventful until this episode. She had three prior full-term pregnancies and one miscarriage without similar symptoms.

Stephanie L. Lee

She was admitted to the hospital for evaluation. Visual fields showed bilateral hemianopsia. Initial laboratory testing demonstrated secondary hypothyroidism with a low thyroid-stimulating hormone of 0.03 µU/mL and free thyroxine index of 0.9 ng/dL (normal, 1-4 ng/dL), low gonadotropins (luteinizing hormone < 0.1 mU/mL, follicle-stimulating hormone < 0.1 mU/mL), elevated prolactin of 283 ng/mL and normal adrenal function (adrenocorticotropic hormone of 15 pg/mL and a morning cortisol of 11 µg/dL).

The laboratory testing showed secondary hypothyroidism. The high prolactin level and low gonadotropin levels were judged physiologically appropriate at 39 weeks of gestation.

The patient had an urgent cesarean section after the administration of stress-dose glucocorticoid therapy with the uneventful birth of a healthy baby. Three days later, she had symptomatic worsening of her vision with concordant with progression of her visual field deficits.

Imaging, treatment

An MRI of the pituitary with and without contrast was performed that showed the mass was stable in size measuring approximately 1.7 x 1.2 x 1.8 cm (CC x AP x TV; Figure). The pituitary mass was homogeneously enhancing after gadolinium infusion. An enhancement of the dura adjacent to the sella, the “dural tail sign,” was noted (Figure 1D).

The neuroradiology assessment was that the mass was likely a pituitary macroadenoma. Because of the worsening of her vision and the radiologic diagnosis of a pituitary adenoma, the patient immediately underwent a transsphenoidal debulking of the pituitary mass. The pathology revealed a diffuse infiltrate of lymphocytes, macrophages and plasma cells consistent with a lymphocytic hypophysitis without evidence of a pituitary adenoma. Postoperatively, her visual fields normalized, and she developed transient diabetes insipidus. Six months after the surgery, the patient has normal visual fields, adrenal function and posterior pituitary function. She remains on levothyroxine therapy for secondary hypothyroidism.

Diagnosing lymphocytic hypophysitis

Lymphocytic hypophysitis is an uncommon inflammatory/autoimmune disorder that primarily involves the pituitary gland and the pituitary stalk. The most common presenting symptom of the condition is headache, which can be retro-orbital or bitemporal. Other symptoms and signs are due to hypopituitarism with anterior and posterior pituitary hormone deficiencies. If there is mass effect on the optic chiasm, vision may be impaired, usually with a bitemporal hemianopsia. If the cavernous sinus is involved, patients may have diplopia and orbital pain.

Lymphocytic hypophysitis is most commonly diagnosed in women during pregnancy or in the postpartum period but can occur in either sex at any age. Lymphocytic hypophysitis can be associated with other types of autoimmune disease.

Magnified T1-weighted MRI images of the sella with and without gadolinium. Coronal (A, B) and sagittal (C, D) images through the sella before (A, C) and after (B, D) gadolinium infusion. The pituitary is replaced by an enlarged mass (yellow arrow) that displaces the optic nerve superiorly. This mass is isointense as the brain on T1-weighted images without gadolinium enhancement (A, C). The mass enhances diffusely after gadolinium administration (B, D). The is enhancement of the adjacent dura (D) is called the “dural tail sign” (red arrow).

This case demonstrates most of the MRI changes of hypophysitis. MRI scan characteristics of hypophysitis include diffuse, ill-defined, symmetrical enlargement of the pituitary often described as “pear-shaped,” thickened but nondeviated pituitary stalk, and isointensity with the brain gray matter on T1-weighted images.

With gadolinium administration, the pituitary has marked homogeneous or heterogeneous enhancement with a strip of enhanced tissue along the dura mater, called a dural tail sign. Although this dural enhancement has been proposed to be specific for hypophysitis, a dural tail is rarely reported in MRI scans of hypophysitis. This dural enhancement was initially described and associated with meningioma. When the dural tail sign is seen and associated with a sellar mass, it is associated 30% of the time with pituitary adenomas, but also with sellar meningioma, pituitary apoplexy and hypophysitis.

The dural tail sign alone is not specific enough to make a diagnosis of lymphocytic hypophysitis. Although the endocrine consult judged the MRI changes to be consistent with a hypophysitis and not a pituitary adenoma, the change in clinical status with worsening of the patient’s visual fields warranted surgical intervention. Medical treatment with tapering high-dose corticosteroids is the initial treatment for symptomatic hypophysitis without vision loss to treat the inflammatory process. As in this case, if there is vision loss, surgical debulking of the enlarged pituitary is recommended.