Empty sella

Last revised by Dr Francis Deng on 27 Jul 2021

An empty sella, also known as an empty pituitary fossa, refers to the appearance of the sella turcica when the pituitary gland appears shrunken or invisible and CSF fills the space instead. It is commonly an incidental finding of no clinical significance, but there exists a well-established association with idiopathic intracranial hypertension.

The finding of pituitary gland height loss and CSF protrusion into the sella turcica occurs in gradations (see pituitary grading), resulting in variability in descriptive terminology. At the less restrictive end of the spectrum, some authors use empty sella to refer to any degree of pituitary height loss/concavity (at least grade II) 11. More reasonable authors define empty sella as at least 33% pituitary height loss (grade III) 14. Most strictly, some authors reserve the term empty sella for when there is essentially no visible pituitary tissue and the fossa is at least a little enlarged (grade V). 

Higher grades are termed complete/total empty sella and lower grades are termed partially/partial empty sella. The border between these two categories is commonly defined in the endocrinology literature in the following manner 6,15,16:

  • complete/total empty sella: >50% of the sella filled with CSF; pituitary thickness ≤2 mm
  • partial empty sella: <50% of the sella filled with CSF; pituitary thickness ≥3 mm

It should be noted that the term was originally described in the context of an enlarged fossa seen on plain radiography (or pneumoencephalography, etc.), without a mass being found at surgery.

Historically (and still today), empty sella patients were divided into those with:

  1. primary empty sella (i.e. those without antecedent causes)
  2. secondary empty sella (i.e. those with an identifiable cause, such as prior tumors, radiotherapy, surgery, or hemorrhage)

It is difficult to determine which patients, if any, would fit in the primary category, as it is increasingly believed that these patients represent either patients with elevated CSF pressures who are nonetheless asymptomatic or patients who have had a previously undiagnosed condition (e.g. idiopathic intracranial hypertension 3lymphocytic hypophysitis 6Sheehan syndrome 9, etc.).

Previously, the term empty sella syndrome was used to denote patients with headaches and visual disturbances. It is now thought that many of these patients have idiopathic intracranial hypertension and that the empty sella is actually secondary to elevated CSF pressures.

As has been alluded to above, it is difficult to pin down the epidemiology for empty sella without contamination by patients with idiopathic intracranial hypertension. As such most publications report a strong female predilection, with obesity also frequently reported.

Although many patients with so-called primary empty sella are entirely asymptomatic and endocrinologically normal, increasingly recognized are variable hypopituitarism (e.g. growth hormone deficiency 8) and hyperprolactinemia 7. Whether these conditions are secondary to the empty sella or, rather, both the empty sella and endocrinopathy represent the sequelae of previous disease, is unclear.

Herniations of suprasellar structures into the empty sella may occur, especially when the empty sella is secondary in origin, and most of these cases present with visual disturbances due to herniation of the optic chiasm 12

An empty sella is believed to result from herniation of the arachnoid space into the pituitary fossa through a deficient diaphragma sellae, found in 20% of the population 4,5. Although this can occur in patients with normal intracranial hydrodynamics/hemodynamics, it is more likely to be associated with idiopathic intracranial hypertension. A common underlying pathology to cases of empty sella both with and without intracranial hypertension may be hemodynamically significant transverse sinus stenosis, which results in altered CSF absorption and expansion of CSF spaces 13.

Lateral skull x-ray appearance is indistinguishable from those of patients with a pituitary mass (e.g. pituitary macroadenoma). The fossa is enlarged to a variable extent with thinned remodeled margins but no evidence of a destructive process.

CT generally shows a fossa filled with CSF, again of variable size. If thin-section imaging is obtained the infundibulum may be seen coursing through the CSF-filled sella (see below).

MRI is the modality of choice for confirming the diagnosis, although it is often unnecessary. It will demonstrate the sella to be filled with CSF and the infundibulum can be seen to traverse the space, thereby excluding a cystic mass. This is known as the infundibulum sign 1.

Trying to assess the significance of an incidentally identified empty sella can be difficult, especially if no pertinent clinical notes are available. The likelihood of it representing undiagnosed intracranial hypertension correlates with the patient's age and gender (middle age and female), orbital findings (flattened globes and optic nerve sheath prominence), and subcutaneous fat thickness as a marker of weight, although no cut-off measurements are available 11.

As an isolated finding, they do not require treatment and have little clinical significance.

It is interesting to note that when an empty sella is seen in the context of idiopathic intracranial hypertension, successful treatment of the condition has been reported to result in resolution of the empty sella, with the pituitary regaining a larger more normal size 2.

The term 'empty sella' was coined in 1951 by Busch as a result of an autopsy study of 40 cadavers 4,10.

The main differential is that of other cystic lesions of the pituitary region, all of which displace the infundibulum to the sides of the fossa (i.e. infundibulum sign is absent 1). Nonetheless, the differential includes:

  • arachnoid cyst
    • very similar in appearance, plus mass effect on the infundibulum
    • on high-resolution imaging, the margins of the cyst may be visible superiorly
  • Rathke cleft cyst
    • usually do not exactly follow CSF signal
    • may contain a small T2-hypointense dot (cyst with dot sign)
  • craniopharyngioma
    • usually do not exactly follow CSF signal
    • usually have visible solid components
    • often calcified
  • cystic pituitary macroadenoma
    • usually do not exactly follow CSF signal
    • usually have visible solid components
  • epidermoid
    • usually do not exactly follow CSF signal
    • demonstrate restricted diffusion

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Cases and figures

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  • Case 6
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  • Case 7
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  • Case 8
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  • Case 9: secondary empty sella with herniations within
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