A partially empty sella is a condition where the pituitary gland appears flattened or displaced within its protective bony cavity at the base of the skull. This occurs because cerebrospinal fluid, the liquid that surrounds the brain and spinal cord, fills part of this space. It is often discovered incidentally during imaging scans performed for other reasons, and in many cases, it does not cause any symptoms or require specific treatment. Its origins can vary from natural anatomical variations to consequences of other medical conditions.
Understanding the Sella Turcica and Empty Sella
The sella turcica is a saddle-shaped depression located in the sphenoid bone at the base of the skull. This bony structure provides a secure housing for the pituitary gland, protecting it from injury. Normally, the pituitary gland occupies most of this space, with only a small amount of cerebrospinal fluid present.
The term “empty sella” is misleading because the sella turcica is not truly empty; it is filled with cerebrospinal fluid. This fluid exerts pressure on the pituitary gland, causing it to shrink or flatten against the walls of the sella. A “partially empty sella” means some of the pituitary gland remains visible on imaging scans, though compressed or displaced. In contrast, a “completely empty sella” indicates the gland is barely, if at all, discernible, with the cavity almost entirely filled with fluid.
Primary Causes of Partially Empty Sella
Primary empty sella syndrome arises when there is no identifiable underlying medical condition. This form occurs due to a small defect or weakness in the diaphragm sellae, a membrane that typically covers the sella turcica and separates the pituitary gland from the fluid-filled space above it. This defect allows the arachnoid membrane, which contains cerebrospinal fluid, to bulge down into the sella turcica.
This condition often develops spontaneously. It is more commonly observed in middle-aged women, particularly those who are obese or have high blood pressure. Elevated intracranial pressure, such as idiopathic intracranial hypertension or pseudotumor cerebri, can also contribute by increasing cerebrospinal fluid pressure, pushing it into the sella.
Secondary Causes of Partially Empty Sella
Secondary empty sella syndrome occurs when the sella becomes partially empty due to a pre-existing medical condition, injury, or treatment. One common scenario involves the regression of a pituitary tumor. After treatments like radiation therapy or surgery, or even spontaneous necrosis, a tumor can shrink, leaving behind a cavity that fills with cerebrospinal fluid.
Another cause is Sheehan’s syndrome, a rare condition involving postpartum pituitary necrosis, where severe blood loss during childbirth leads to damage and shrinkage of the pituitary gland. Trauma to the head or surgical procedures near the pituitary region can also directly injure the gland, leading to its atrophy and subsequent filling of the sella with fluid. Inflammatory conditions affecting the pituitary or surrounding brain structures, as well as hydrocephalus, which involves an excess of cerebrospinal fluid, can increase pressure within the skull and contribute to a partially empty sella.
Recognizing and Managing Partially Empty Sella
A partially empty sella is most frequently identified incidentally during magnetic resonance imaging (MRI) or computed tomography (CT) scans of the head. Many individuals with a partially empty sella experience no symptoms directly attributable to the condition. However, if symptoms are present, they are typically related to pituitary dysfunction, such as hormonal imbalances. These can include issues like hypothyroidism, adrenal insufficiency, or hyperprolactinemia, which manifest as fatigue, weight changes, or irregular menstrual cycles.
The diagnostic process involves imaging to confirm the presence of a partially empty sella, followed by hormone tests if there are indications of pituitary dysfunction. If the condition is asymptomatic and pituitary function is normal, no specific treatment is required. Management focuses on addressing any underlying conditions that might have led to a secondary empty sella or treating specific hormone deficiencies if detected. For instance, hormone replacement therapy may be prescribed to correct imbalances.