A partially empty sella is a radiological finding in which the pituitary gland appears flattened or compressed within the sella turcica — the bony cavity at the base of the skull that normally houses the pituitary gland — with cerebrospinal fluid filling the remainder of the space. It is most commonly a benign, incidental finding on brain MRI, but can occasionally be associated with pituitary hormonal abnormalities or symptoms of elevated intracranial pressure that require evaluation and treatment.
Partially empty sella is one of several sellar region findings encountered on brain MRI that must be distinguished from pathological conditions. It is closely related to pituitary tumors in the differential diagnosis of sellar abnormalities, and a prior history of pituitary surgery or apoplexy can produce a secondary empty sella. When occurring in the context of idiopathic intracranial hypertension (IIH), it is part of a broader syndrome that also causes visual pathway compression — related to conditions affecting CSF pressure and circulation.
Causes
Primary: Herniation of the arachnoid membrane
The most common cause is a deficiency or weakness in the diaphragma sellae — the dural membrane that normally forms a roof over the sella turcica. When this covering is incomplete, CSF-filled arachnoid tissue herniates downward into the sella and gradually compresses and flattens the pituitary gland against the sella floor over years. This is the mechanism of primary empty sella syndrome — a benign anatomical variant in the vast majority of cases. It is more common in multiparous women and those with obesity, suggesting that elevated intracranial pressure during pregnancy may stretch and weaken the diaphragma over time.
Secondary causes
Secondary empty sella results from destruction or shrinkage of the pituitary gland itself, leaving a partially empty sella behind. Common causes include prior pituitary tumor treatment (transsphenoidal surgery or radiation therapy), pituitary apoplexy (acute hemorrhage or infarction into a pituitary tumor — a neurological emergency), and spontaneous involution of a pituitary adenoma. Idiopathic intracranial hypertension (IIH / pseudotumor cerebri) — a condition of chronically elevated CSF pressure predominantly affecting obese women of childbearing age — transmits increased pressure into the sella and is an important and treatable secondary cause.
Symptoms
The majority of partially empty sellas are completely asymptomatic and require no treatment beyond baseline evaluation. When symptoms occur, they reflect either pituitary dysfunction or elevated intracranial pressure:
- Headaches: The most commonly reported symptom — though establishing causation is challenging given that headaches are prevalent in the same demographic groups affected by empty sella (obese women of childbearing age).
- Hormonal symptoms: Fatigue, weight changes, menstrual irregularities, decreased libido, and cold intolerance from pituitary gland compression and hypopituitarism. Hyperprolactinemia can occur if the pituitary stalk is kinked by the herniated arachnoid.
- Visual disturbances: Typically from IIH-related papilledema rather than direct chiasm compression — though rarely the optic chiasm can herniate into the sella alongside the arachnoid, causing visual field defects.
- IIH symptoms: Pulsatile tinnitus (a whooshing sound in the ears synchronous with the heartbeat), transient visual obscurations, and papilledema on fundoscopic examination — symptoms of chronically elevated intracranial pressure that require urgent ophthalmological evaluation to protect vision.
Diagnosis
MRI of the pituitary with gadolinium contrast — using dedicated thin-slice coronal and sagittal sequences through the sella — is the definitive imaging study. The characteristic appearance is a sella filled with CSF signal (dark on T1, bright on T2), with the pituitary gland flattened against the sella floor and the pituitary stalk typically remaining centrally positioned. This central stalk position helps distinguish empty sella from pituitary tumors that typically displace the stalk laterally. The optic chiasm position is assessed to exclude chiasmal herniation.
A comprehensive pituitary hormone panel — including morning cortisol, thyroid function (TSH, free T4), prolactin, IGF-1 (growth hormone surrogate), LH, FSH, and gonadal hormones — establishes baseline pituitary function. Formal visual field testing and fundoscopic examination for papilledema are essential when IIH is suspected. If IIH is confirmed, lumbar puncture opening pressure measurement documents the degree of intracranial hypertension and guides treatment intensity.
Classification
Empty sella is classified by underlying cause, which determines management:
- Primary empty sella: Arachnoid herniation through an incomplete diaphragma sellae — no prior pituitary pathology. The most common and typically benign form. Requires hormonal assessment and reassurance in most cases.
- Secondary empty sella: Resulting from prior pituitary tumor treatment, surgery, radiation, or apoplexy. Pituitary hormone deficiencies are more common and require systematic evaluation and replacement.
- IIH-associated empty sella: Occurring in the context of idiopathic intracranial hypertension — the underlying elevated CSF pressure requires treatment to prevent progressive vision loss.
Treatments
Most patients with an incidentally discovered partially empty sella require no specific treatment beyond reassurance and a baseline hormonal assessment. Periodic follow-up with hormonal testing and interval imaging is appropriate.
Hormone replacement therapy:
When pituitary hormone deficiencies are identified, targeted replacement is initiated: levothyroxine for hypothyroidism, hydrocortisone for adrenal insufficiency (which must be identified and treated first as it is potentially life-threatening), testosterone or estrogen/progesterone for hypogonadism, and growth hormone for confirmed GH deficiency in appropriate candidates. Hyperprolactinemia from stalk kinking may respond to dopamine agonist therapy (cabergoline).
Treatment of idiopathic intracranial hypertension (IIH):
When empty sella occurs in the context of IIH, treating the underlying elevated CSF pressure is essential to protect vision and relieve symptoms. First-line treatment includes weight loss (10% body weight reduction significantly reduces intracranial pressure) and acetazolamide (a carbonic anhydrase inhibitor that reduces CSF production). Topiramate is an alternative with weight loss benefits. For vision-threatening papilledema that does not respond to medical management, surgical CSF diversion — optic nerve sheath fenestration (directly relieves pressure on the optic nerve) or CSF shunting (ventriculoperitoneal or lumboperitoneal shunt) — is performed urgently to prevent permanent visual loss.
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