Patients with arachnoid cysts will most likely never show symptoms, even in cases where the cyst is large. Therefore, while the presence of symptoms may provoke further clinical investigation, symptoms independent of further data cannot, and should not be, interpreted as evidence of a cyst’s existence, size or location.

• They usually develop in utero, during fetal life, but they can also develop after trauma, surgeries or CNS infections;
• Usually arachnoid cysts are asymptomatic, but in a few patients it may cause symptoms;
• Symptoms vary by the size and location of the cyst, though small cysts usually have no symptoms and are discovered only incidentally.;
• Larger cysts are more likely to present with symptoms as they may compress surrounding structures.
• These symptoms usually are:
  • Headache;
  • Nausea/Vomiting;
  • Seizures;
  • Skull/spine deformation;
  • Developmental delays;
  • Obstructive hydrocephalus;
  • Hearing loss;
  • Head bobbing;
  • Visual changes.^[1][2]
• The symptoms listed above may develop in kids after they are born, or in patients after they have suffered head trauma, CNS infections. This last group of patients usually does not present with skull/spine deformation or developmental delays, as they have already fully developed after childhood but they can present with behavioral changes.
• Spinal meningeal cysts, a rare form of arachnoid cysts, usually present with progressive spastic or flaccid paraparesis or quadriparesis in the second decade of life. 10% may present with monoparesis.^[3]