Arachnoid Cyst F090

ICD coding

• ICD-10-AM: Brain: Acquired G93.0; Spinal cord: G96.1.

Brief description

A cyst is a non-cancerous fluid-filled sac surrounded by a membrane. An arachnoid cyst develops within the layers of the arachnoid membrane, which surround the brain and spinal cord. Most arachnoid cysts are symptomatic and discovered incidentally but larger cysts or those in critical locations may cause symptoms or signs. 

Confirming the diagnosis

To confirm the diagnosis, imaging is usually required (MRI or CT scan of the brain/spinal cord). 

To establish this diagnosis, the assessment and/or management may involve consultation with a neurologist or neurosurgeon. General practitioners are able to confirm this diagnosis with imaging results.

Additional diagnoses covered by these SOPs

• Arachnoid cyst of the brain
• Arachnoid cyst of the spinal cord

Conditions not covered by these SOPs

• Arachnoid cysts associated with autosomal dominant polycystic kidney disease *
• Intra-cerebral cysts #
• Leptomeningeal cysts #
• Cerebral meningioma *
• Acoustic neuroma *
• Malignant neoplasm of the brain *
• Soft tissue sarcoma *
• Spinal adhesive arachnoiditis * 

* another SOP applies

^# non-SOP condition

Clinical onset

Many arachnoid cysts are asymptomatic, and the onset will be when the condition was first diagnosed via imaging. Symptomatic cysts can present with symptoms based on their size and location (e.g. headaches, seizures, weakness, numbness, memory loss, back or neck pain etc). 

Clinical worsening

Most arachnoid cysts are asymptomatic and do not require treatment. Therefore, clinical worsening is generally not be an issue.  However, cysts can expand in size and cause pressure effects and location specific symptoms. Clinical worsening can occur due to many of the same causal factors related to clinical onset. Additionally, the inability to obtain appropriate surgical intervention for an expanding arachnoid cyst could also worsen the condition.