A partial empty sella is a finding on a brain scan, often an incidental discovery with no clinical significance. The term describes an anatomical variation where the pituitary gland, the body’s master hormone regulator, appears compressed or flattened. This flattening occurs because cerebrospinal fluid (CSF) has partially filled the bony chamber that houses the gland, the sella turcica. This article clarifies the meaning of this finding and determines when a partial empty sella warrants further investigation.
Defining the Sella Turcica and Empty Sella
The sella turcica, which translates from Latin as “Turkish saddle,” is a saddle-shaped depression in the sphenoid bone at the base of the skull. This structure serves as a protective bony seat for the pituitary gland, also called the hypophysis. The pituitary gland is a central component of the endocrine system, controlling the release of hormones that regulate growth, metabolism, and reproduction.
An “empty sella” occurs when the subarachnoid space, containing cerebrospinal fluid (CSF), extends downward into the sella turcica. This influx of CSF compresses the pituitary gland, causing it to appear shrunken or flattened on imaging tests like Magnetic Resonance Imaging (MRI). The term “empty” is misleading because the sella is not truly hollow; it is partially filled with CSF and a compressed pituitary gland.
The finding is categorized into two types: partial and complete. A partial empty sella is diagnosed when CSF occupies less than 50% of the sella turcica volume, and the pituitary gland tissue maintains a thickness of 3 millimeters or greater. A complete empty sella involves more than 50% of the sella being filled with CSF, with the pituitary gland often flattened to 2 millimeters or less.
Primary and Secondary Causes
The development of a partial empty sella is divided into two main categories: primary and secondary. Primary empty sella (PES) is the more common type and occurs without any identifiable underlying medical cause. This is thought to result from a small, often congenital, defect in the diaphragma sellae, the membrane that normally seals the top of the sella.
This defect allows the subarachnoid space to herniate into the sella, and the pressure of the CSF gradually flattens the pituitary gland. PES is frequently associated with conditions that increase intracranial pressure, such as obesity or idiopathic intracranial hypertension, and is observed more often in women. In most cases of PES, the pituitary gland continues to function normally despite its flattened appearance.
Secondary empty sella (SES) is caused by a specific, identifiable medical condition that damages or shrinks the pituitary gland. These causes include prior pituitary surgery, radiation therapy to the head, or conditions that cause bleeding or inflammation in the gland, such as pituitary apoplexy or hypophysitis. The regression or treatment of a pituitary tumor that previously occupied the space can also result in an SES. Secondary cases are more likely to be associated with significant hormonal dysfunction.
Addressing the Core Question: Is Partial Empty Sella Normal?
A primary partial empty sella is a common finding and is generally considered an incidental radiological discovery. It is often found when a brain scan is performed for an unrelated reason, such as a headache. Estimates suggest that some degree of primary empty sella may be present in 8% to 35% of the general population.
The high prevalence in asymptomatic individuals underscores why a partial empty sella is usually dismissed by clinicians as a benign anatomical variation. When it is primary and the patient has no associated symptoms, no specific treatment or monitoring is required. The pituitary gland, even when partially compressed, often retains enough functional tissue to produce a standard range of hormones.
The risk of hormonal disturbance is significantly lower in patients with a partial empty sella compared to those with a complete empty sella. Studies have shown that a partial empty sella is less likely to be associated with pituitary insufficiency. The finding in isolation, particularly in the absence of hormonal or visual disturbance, does not affect life expectancy or overall health.
Symptoms and When Investigation is Needed
While a partial empty sella is often benign, the presence of certain symptoms necessitates a thorough medical investigation. Symptoms that indicate a potential medical concern are typically related to pituitary dysfunction or increased intracranial pressure. The most common symptom associated with empty sella is chronic headaches, which may be linked to CSF pressure.
Other signs that require investigation include:
- Visual field defects, such as a loss of peripheral vision, which can occur if the optic chiasm is pressed downward into the empty sella.
- Symptoms of hormonal imbalance, collectively known as hypopituitarism.
These hormonal symptoms can include fatigue, irregular menstrual periods, decreased sex drive, or erectile dysfunction.
When symptoms are present, the diagnostic process begins with a comprehensive hormonal panel to assess pituitary function. This evaluation checks for thyroid-stimulating hormone, cortisol, prolactin, and sex hormones to determine if any endocrine axes are underactive. Specialized MRI protocols are used to confirm the diagnosis and rule out secondary causes or microadenomas that might mimic the condition. If a hormonal deficiency is identified, treatment involves hormone replacement therapy tailored to the specific hormones that are lacking.