What is a partially empty sella turcica on brain MRI?

What is a Partially Empty Sella Turcica on Brain MRI?

A partially empty sella turcica is a common radiographic finding in which cerebrospinal fluid partially fills the pituitary fossa, compressing the pituitary gland against the sellar floor—this appearance is frequently a normal age-related variant, particularly in women, but warrants systematic endocrine evaluation because 29–40.5% of patients harbor at least one pituitary hormone deficiency despite being asymptomatic. 1

Radiographic Definition and Normal Variants

• The partially empty sella describes a pituitary gland that does not fully occupy the sella turcica on MRI, with cerebrospinal fluid visible in the remaining space. 2
• This finding increases significantly with age and is more prominent in women, representing a normal physiologic variant in many individuals. 2
• On routine sagittal T1-weighted MRI sequences, the partially empty sella is commonly observed even in neurologically normal patients and is usually of no clinical significance when discovered incidentally. 2
• The appearance can result from herniation of the subarachnoid space through a defect in the diaphragma sellae, allowing CSF to compress the pituitary gland. 1

Clinical Significance and Risk Stratification

• Despite the absence of symptoms, 29–40.5% of patients with incidentally discovered empty or partially empty sella have at least one pituitary hormone deficiency, making systematic endocrine screening essential. 1
• The negative predictive value of symptom absence is only approximately 71%, meaning roughly 29% of asymptomatic patients still harbor hormonal deficits. 1, 3
• Male sex (P = 0.02), clinical suspicion prompting evaluation (P < 0.001), and history of traumatic brain injury (P = 0.003) are significant predictors of hypopituitarism in patients with empty sella. 1
• Progression from a partial to a total empty sella correlates with hormonal deterioration (P = 0.006), necessitating serial imaging and repeat hormone panels. 1, 3

Recommended Endocrine Evaluation

All patients with a partially empty sella should receive a comprehensive baseline pituitary hormone panel at first presentation, regardless of symptoms:

• Adrenal axis (highest priority): Obtain morning (≈8 AM) serum cortisol and ACTH; hypocortisolism occurs in 13.5–17.7% of cases and can be life-threatening if unrecognized during physiologic stress. 1, 3
• Thyroid axis: Measure free thyroxine (FT4) and TSH; central hypothyroidism is present in 2.8–29.2% of patients, with markedly higher rates when the finding is symptomatic rather than incidental. 1
• Gonadotroph axis: Assess LH, FSH, and appropriate sex steroids (testosterone in males, estradiol in females as needed); hypogonadism affects 8.5–50.4% of patients. 1
• Growth hormone axis: Measure IGF-1 to screen for GH deficiency, which occurs in 12.5–20.4% of cases; however, approximately 20% of affected adults—particularly males—maintain normal age-adjusted IGF-1 levels, limiting screening sensitivity. 1
• Prolactin axis: Measure serum prolactin; hyperprolactinemia occurs in 2.9–15.7% of patients and may reflect stalk effect or medication use rather than prolactinoma. 1

Dynamic Testing Indications

• If morning cortisol is low (generally <5–10 µg/dL), confirm adrenal insufficiency with dynamic testing such as insulin-tolerance test or cosyntropin stimulation test. 1
• A cortisol level <3 µg/dL is sufficient for diagnosis and does not require confirmatory dynamic testing; initiate hydrocortisone replacement immediately. 1
• Select patients may require dynamic testing for growth hormone deficiency after correction of other pituitary hormone deficits. 1

Imaging Recommendations

• Perform dedicated pituitary MRI using thin slices (<2–3 mm) with pre- and post-gadolinium sequences in coronal, axial, and sagittal planes to identify mass lesions, hemorrhage, or infiltrative processes. 1
• Serial imaging is indicated for patients with partial empty sella, as progression to total empty sella can precipitate further hormonal decline. 1, 3

Follow-Up and Monitoring

• Repeat the full pituitary hormone panel 1–2 years after initial assessment, or sooner if new clinical signs emerge, because hypopituitarism can develop without detectable tumor growth. 1
• New hormone deficiencies can arise at an incidence of 1.2–2.4 per 100 person-years even without radiographic progression. 1
• Conduct immediate repeat testing if surveillance imaging shows enlargement of any pituitary lesion or progression from partial to total empty sella. 1

Associated Conditions to Consider

• Idiopathic intracranial hypertension: Chronic elevation of intracranial pressure causes bony enlargement of the sella turcica, contributing to its partially empty appearance; patients are typically younger (mean age 36 years), report headache (93%) and visual complaints (66%), and show greater scalp and neck soft-tissue thickness on MRI. 4, 5
• Central diabetes insipidus: Present in approximately 0.9–1.7% of patients with empty sella syndrome; screen through history and baseline electrolytes. 1
• CSF rhinorrhea: Occurs in 0.9–1.7% of cases due to herniation of subarachnoid space through a sellar floor defect. 1
• Visual field defects: Can develop when the optic chiasm is compressed or intracranial pressure is elevated. 1

Critical Pitfalls to Avoid

• Do not assume normal pituitary function based solely on symptom absence; the negative predictive value is only 71%, and 29–40.5% of asymptomatic patients have hormone deficiencies. 1, 3
• Do not overlook adrenal insufficiency, which occurs at comparable rates in incidental (13.5%) and symptomatic (17.7%) presentations and carries risk of life-threatening adrenal crisis during stress. 1, 3
• Do not discontinue hydrocortisone to repeat cortisol measurements once a markedly low level has confirmed the diagnosis. 1
• Do not use random (non-timed) cortisol measurements, as they have no diagnostic utility for adrenal insufficiency. 1
• Do not rely on single random growth hormone measurements, which are diagnostically unreliable. 1
• Do not use serum total T3 or free T3 for diagnosing central hypothyroidism. 1