Arachnoid Cysts

What Are Arachnoid Cysts?

Arachnoid cysts are closely related to the structure of the brain’s protective membranes. Both the brain and spinal cord are covered by three layers:

1. Pia mater – the innermost layer, rich in blood vessels, directly covering the brain.
2. Arachnoid membrane (arachnoidea) – the intermediate layer, also known as the veil-like membrane.
3. Dura mater – the outermost tough, protective layer.

What Causes Arachnoid Cysts?

The exact cause of arachnoid cysts is unknown. Scientists believe that most arachnoid cysts result from developmental abnormalities due to an unexplained splitting or rupture of the arachnoid membrane.

According to medical literature, arachnoid cysts are more frequently observed in children whose parents also have arachnoid cysts, suggesting a possible genetic predisposition in some individuals.

In certain cases, arachnoid cysts develop in conjunction with underdeveloped brain regions (hypoplasia), particularly affecting the temporal lobes. If a brain region does not fully occupy the skull space, a "gap" may form, leading to an arachnoid cyst.

Conversely, an existing arachnoid cyst can impede normal brain development by exerting pressure on adjacent structures. However, the precise reasons for these occurrences remain unclear in medical science.

Who Is More Likely to Develop Arachnoid Cysts?

Arachnoid cysts are more commonly found in males than females. They can be diagnosed at any age and occur across all racial and geographical populations. They are also the most common type of intracranial cyst.

Since many arachnoid cysts remain asymptomatic, their prevalence in the general population is difficult to determine.

Where Do Arachnoid Cysts Develop in the Skull?

Arachnoid cysts most frequently occur in the following brain regions:

1. Middle cranial fossa (where the temporal lobes are located).
2. Suprasellar region (near the third brain ventricle).
3. Posterior cranial fossa (home to the cerebellum, brainstem, and medulla oblongata).

Arachnoid cysts are classified based on their location, such as:

• Right temporal arachnoid cyst
• Arachnoid cyst in the right middle cranial fossa

What Symptoms or Complications Can Arachnoid Cysts Cause?

In most cases, arachnoid cysts are congenital and do not cause symptoms (asymptomatic cysts). These cysts do not increase intracranial pressure, either due to their small size or stable fluid volume, meaning patients remain unaware of their presence unless detected incidentally during imaging tests performed for other reasons.

However, in rare cases, arachnoid cysts can cause significant problems:

• Head trauma can rupture small blood vessels within the cyst walls, leading to bleeding into the brain or inside the cyst itself.
• Patients with asymptomatic arachnoid cysts are at higher risk of severe intracranial bleeding after head trauma. If significant hemorrhage occurs, emergency surgery may be required to remove the cyst and blood clot.

Symptomatic Arachnoid Cysts

Larger cysts or those exerting pressure on surrounding brain structures may cause:

• Headaches, nausea, and vomiting
• Dizziness
• Epileptic seizures
• Cerebrospinal fluid circulation disorders (hydrocephalus)
• Developmental delays and behavioral changes
• Loss of voluntary movement control (ataxia)
• Balance disturbances
• Weakness or paralysis on one side of the body (hemiparesis)

In children, increased intracranial pressure due to arachnoid cysts may result in:

• Skull deformities
• Enlarged head size (macrocephaly)

Cysts in the suprasellar region may lead to vision disturbances and hormonal imbalances, affecting:

• Menstrual cycles
• Growth rates
• Sexual development

What Should You Do If Diagnosed with an Arachnoid Cyst?

If you or a loved one has confirmed or suspected arachnoid cysts, a neurosurgical consultation is necessary.

We offer in-person and remote consultations via video calls. Appointments can be scheduled online, via phone, or email. Contact us to arrange a remote consultation.

Can Arachnoid Cysts Occur in the Spine?

Yes, spinal (arachnoid) cysts are less common than intracranial cysts, but they can form within the spinal canal from the arachnoid membrane of the spinal cord.

Symptoms of Spinal Arachnoid Cysts:

• Progressive limb weakness (paresis)
• Tingling/numbness in arms or legs
• Abnormal spinal curvature (scoliosis)
• Back pain
• Involuntary muscle spasms (spasticity)

How Are Arachnoid Cysts Diagnosed?

Arachnoid cysts can be detected using imaging studies, such as:

• Computed Tomography (CT/DT)
• Magnetic Resonance Imaging (MRI)

Cysts are often found incidentally during imaging scans performed for unrelated conditions. However, if symptoms arise, diagnostic imaging can help identify their cause.

How Are Symptomatic Arachnoid Cysts Treated?

Treatment is only required for arachnoid cysts causing symptoms. If the cyst is discovered incidentally and does not cause health issues, no intervention is necessary.

However, if symptoms develop later, the relationship between the cyst and symptoms can be reassessed.

Surgical Treatment Options for Symptomatic Arachnoid Cysts:

1. Cyst wall removal and communication with surrounding spaces (cyst fenestration)
2. Drainage via a special tube to relieve pressure (cyst shunting surgery)

Fenestration can be performed using:

• A small skull opening (craniotomy)
• Minimally invasive endoscopic techniques

Endoscopic surgery reduces complication risks and shortens recovery time.

Shunting surgery involves draining fluid from the cyst into the abdominal cavity to relieve pressure inside the cyst.

For spinal arachnoid cysts, treatment may include:

• Complete cyst removal (resection)
• Fenestration
• Shunting procedures

What Is the Prognosis for Arachnoid Cysts?

Surgical treatment of symptomatic arachnoid cysts typically results in complete symptom resolution. In cases where surgery is not possible, symptomatic management may be required.

If you are considering surgery with us, you can read patient testimonials from both Latvian and international patients.