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Arachnoid Cysts

Original Editor - Nivedita Raut

Top Contributors - Nivedita Raut, Khloud Shreif, Kim Jackson and Kirenga Bamurange Liliane  

Introduction: Understanding Arachnoid Cysts

Arachnoid cysts are cerebrospinal fluid (CSF) filled sacs that develop between the brain or spinal cord and the arachnoid membrane, one of the three layers covering the central nervous system. They can be congenital (present at birth) or acquired through trauma, infection, or surgery. Though many cysts are asymptomatic and discovered incidentally during MRI or CT scans, larger cysts can exert pressure on nearby neural structures, leading to symptoms such as headaches, seizures, motor issues, or cognitive impairments.[1][2]

Image 1- MRI of a 25 year old female with frontotemporal arachnoid cyst.

Anatomy

The brain and spinal cord are encased within three layers of protective membranes called the meninges. These layers, from outermost to innermost, are the dura mater, arachnoid mater, and pia mater. The primary function of the meninges, including the arachnoid mater, is to provide physical protection and support to the brain and spinal cord.

The dura mater is the thickest layer, made of dense connective tissue, and adheres firmly to the inside of the skull and vertebrae. Just beneath the dura lies the arachnoid mater, a delicate, web-like membrane. The innermost layer, the pia mater, is a very thin, transparent membrane that adheres directly to the surface of the brain and spinal cord.[3][4]

Between these layers are three important spaces: the epidural space (between the dura and skull or vertebrae), the subdural space (between the dura and arachnoid), and the subarachnoid space (between the arachnoid and pia). The subarachnoid space is filled with cerebrospinal fluid, playing a crucial role in cushioning and protecting the brain and spinal cord from injury.

An arachnoid cyst forms within the arachnoid mater, typically in the subarachnoid space. These cysts occur when the arachnoid membrane splits or duplicates, trapping CSF inside. Arachnoid cysts can develop anywhere along the brain or spinal cord but are most commonly found in areas like the Sylvian fissure in the brain or along the spinal cord. Though often asymptomatic, they may cause symptoms if they grow large enough to press on nearby neural structures.[5]

Etiology and Presentation

Arachnoid cysts are benign, non-neoplastic fluid collections within the arachnoid mater layer of the meninges, accounting for about 1% of all intracranial space-occupying lesions.[6]Most cysts are congenital. These develop due to an error in embryonic development, particularly affecting the arachnoid membrane, leading to CSF entrapment with a male predominance, showing a male-to-female ratio of approximately 2:1 in both adults and children.[7][8] Secondary arachnoid cysts may result from traumatic brain injury, infections like meningitis, or complications post-surgery, leading to localized fluid buildup between the arachnoid layers. These cysts typically contain clear, colorless fluid resembling CSF .

Arachnoid cysts in the spinal canal, either subdurally or in the epidural space are typically found in the thoracic region, often on the dorsal side of the spinal cord. They may arise from congenital or acquired defects and are typically extradural. Intradural spinal arachnoid cysts[9] are linked to congenital deficiencies in the arachnoidal trabecula or result from adhesions caused by trauma or infections. Microscopically, their walls consist of a splitting of the arachnoid membrane, forming an inner and outer layer around the cyst.

Typical Sites and Clinical Manifestations

Middle Cranial Fossa and Sylvian Fissure

Arachnoid cysts are most commonly found in the middle cranial fossa, specifically within the temporal lobe or Sylvian fissure, accounting for 50-60% of cases in adults. Gallassi's classification[10] categorizes these cysts into three types based on size: small, medium, and large. Symptomatic cysts often present with headaches, seizures, and motor deficits, typically as a result of cyst enlargement exerting mass effect on surrounding structures. Although less common, symptoms may also include epilepsy, nausea, dizziness, and cognitive impairment. Notably, juvenile cysts can grow over time, potentially compressing the middle cerebral artery and affecting temporal lobe development. Bitemporal arachnoid cysts are rare and may require screening for glutaric aciduria before surgical intervention.[11][12][13]

Infratentorial: Cerebellopontine Angle and Retrocebellar Regions

Infratentorial arachnoid cysts occur mainly in the pediatric population, comprising about 10% of cases. They are typically located in the retrocerebellar area or cerebellopontine angle. Symptoms vary depending on the cyst's location and associated mass effect. Obstruction of CSF flow can lead to hydrocephalus, resulting in macrocephaly and increased intracranial pressure. Pressure on the cerebellum may cause nystagmus, ataxia, gait disturbances, and headaches. Cysts in the cerebellopontine angle can compress cranial nerves, leading to focal neurological deficits such as facial palsies or hearing loss, which usually resolve post-treatment.[11][12][13]

Suprasellar and Intrasellar Arachnoid Cysts

These cysts account for 10% of arachnoid cysts and are more frequently observed in children. They can obstruct the third ventricle at the foramen of Monroe, leading to hydrocephalus. Endocrine dysfunction, including deficiencies in growth hormone and disturbances in the hypothalamic-pituitary-gonadal axis, may arise. A rare presentation, known as "bobble-head doll syndrome," occurs due to compression of the third ventricle and thalamic nuclei..[11][12][13][14]

Spinal Arachnoid Cysts

Most commonly found in the thoracic and lumbar spine, spinal arachnoid cysts can cause mass effects similar to their intracranial counterparts. They may lead to slowly progressive myelopathy, presenting with ataxia, weakness, and spasticity. If the cyst enlarges or is complicated by hemorrhage, it can result in spinal cord compression..[11][12][13][15]

Diagnosis

Diagnosis of an arachnoid cyst relies primarily on neuroimaging techniques[16], with magnetic resonance imaging (MRI) being the gold standard. MRI provides highly detailed information regarding the cyst's size, location, and its proximity to neural tissues, offering crucial insight into how the cyst might affect surrounding structures.

  • MRI: This imaging modality is favored due to its superior ability to differentiate between cerebrospinal fluid (which fills arachnoid cysts) and adjacent brain or spinal tissues. MRI scans allow for high-resolution visualization, helping clinicians determine whether the cyst is exerting pressure on the brain or spinal cord, which can correlate with symptoms like headaches, seizures, or motor impairments.[17][18] Additionally, functional MRI or advanced sequences like diffusion-weighted imaging can be used to assess any disruption to neural pathways caused by the cyst.
  • CT Scans: Although not as detailed as MRI, computed tomography (CT) scans may also be used in the diagnosis, especially if MRI is not available or in emergency situations. CT scans can help identify the cyst's density, detect any calcifications, or reveal bone erosion in cases where the cyst has expanded significantly.
  • Ultrasound: In prenatal cases, ultrasound can sometimes detect arachnoid cysts, especially when they are larger or located in more easily visualized regions of the fetal brain. This method can provide early detection and allow for further prenatal follow-up with MRI to understand the cyst's impact.[19]
  • Electroencephalogram (EEG): For symptomatic cases involving seizures, an EEG may be used in conjunction with imaging studies to evaluate the electrical activity in the brain. This helps determine whether the cyst is affecting brain function in a way that provokes seizures or other neurological symptoms.[20]

Management

While small cysts may remain undiagnosed throughout life, large or expanding cysts may require surgical intervention to relieve pressure on the brain or spinal cord. Management depends on cyst size and symptoms. Asymptomatic arachnoid cysts are often monitored with regular MRI or CT scans to track growth or the development of symptoms over time. Intervention may not be required unless the cyst enlarges or begins causing neurological issues.[21]

Surgical Management:

  • Endoscopic Fenestration: This minimally invasive technique involves creating small openings in the cyst to allow the fluid to drain into other areas of the brain. It is often the preferred method due to its lower risk of complications and quicker recovery time.[8][22][23][24]
  • Craniotomy with Fenestration: In cases where endoscopic approaches are not feasible, a craniotomy is performed to access the cyst and allow drainage or removal. This method is more invasive but can provide more direct access to larger or deeply located cysts.[25][26]
  • Shunting: A shunt is placed to divert fluid from the cyst into another part of the body, such as the peritoneal cavity. This is typically used for cysts that continually refill with fluid.[27]

Surgical treatment generally yields positive outcomes, with most patients experiencing significant symptom relief after procedures like cyst drainage or removal. Studies report that most of patients benefit from improved motor skills, reduced headaches, and fewer seizures post-surgery.[28] However, outcomes depend on factors such as cyst size, location, and the patient's preoperative condition. Despite the success of surgery, postoperative care is crucial to manage potential complications, including infection, hydrocephalus, or recurrence of the cyst. Long-term follow-up is often necessary to ensure sustained relief and to monitor for any complications.

Physiotherapy Management

For patients experiencing neurological symptoms or after surgical intervention, physiotherapy plays a key role in rehabilitation, focusing on balance, mobility, and managing residual symptoms like muscle weakness or movement difficulties. While the primary treatment for symptomatic arachnoid cysts is neurosurgical, physiotherapy plays an essential role in rehabilitation, symptom management, and functional recovery, especially post-surgery.

  • Post-Surgical Rehabilitation
    • After cyst removal or drainage, patients often experience muscle weakness, balance issues, or coordination impairments. Physiotherapists can design rehabilitation programs that focus on motor retraining, strength restoration, and gait stabilization.[29][30]
  • Motor Control and Strength
    • Arachnoid cysts located near motor regions of the brain, such as the frontal or parietal lobes, may cause hemiparesis or generalized weakness. Post-surgical physiotherapy addresses these deficits with tailored strength-training programs and neuromuscular re-education.
    • Progressive resistance exercises and functional task training (like stair climbing or balance drills) are essential to improving patient outcomes.[31][32]
  • Balance and Vestibular Therapy
  • Chronic Pain Management
    • Chronic headaches or spinal pain may persist in individuals with large cysts or those awaiting surgery. A combination of manual therapy techniques, myofascial release, and postural correction can help alleviate discomfort and restore function.[34][35]
  • Cognitive and Sensory Rehabilitation

References

  1. ↑ Rabiei K, Jaraj D, Marlow T, Jensen C, Skoog I, Wikkelsø C. Prevalence and symptoms of intracranial arachnoid cysts: a population-based study. Journal of neurology. 2016 Apr;263:689-94.
  2. ↑ Vernooij MW, Ikram MA, Tanghe HL, Vincent AJ, Hofman A, Krestin GP, et al. Incidental Findings on Brain MRI in the General Population, New England Journal of Medicine. 2007 Nov 1;357(18):1821-8.
  3. ↑ Shafique S, Rayi A. Anatomy, head and neck, subarachnoid space. StatPearls Publishing, Treasure Island (FL); 2023.
  4. ↑ Alcolado R, Weller RO, Parrish EP, Garrod D. The cranial arachnoid and pia mater in man: anatomical and ultrastructural observations. Neuropathology and applied neurobiology. 1988 Jan 1;14(1):1-7.
  5. ↑ Rabiei K, Tisell M, Wikkelsø C, Johansson BR. Diverse arachnoid cyst morphology indicates different pathophysiological origins. Fluids and Barriers of the CNS. 2014 Dec;11:1-1.
  6. ↑ Cincu R, Agrawal A, Eiras J. Intracranial arachnoid cysts: current concepts and treatment alternatives. Clinical neurology and neurosurgery. 2007 Dec 1;109(10):837-43.
  7. ↑ Al-Holou WN, Yew AY, Boomsaad ZE, Garton HJ, Muraszko KM, Maher CO. Prevalence and natural history of arachnoid cysts in children. Journal of Neurosurgery: Pediatrics. 2010 Jun 1;5(6):578-85.
  8. ↑ 8.0 8.1 Johnson RD, Chapman S, Bojanic S. Endoscopic fenestration of middle cranial fossa arachnoid cysts: does size matter?. Journal of Clinical Neuroscience. 2011 May 1;18(5):607-12.
  9. ↑ Kalsi P, Hejrati N, Charalampidis A, Wu PH, Schneider M, Wilson JR, Gao AF, Massicotte EM, Fehlings MG. Spinal arachnoid cysts: a case series & systematic review of the literature. Brain and Spine. 2022 Jan 1;2:100904.
  10. ↑ Santos A, Viegas AF, Porto LM, Gomes A, Nascimento E. Arachnoid Cyst: An Asymptomatic Exuberance. Cureus. 2022 Nov;14(11).
  11. ↑ 11.0 11.1 11.2 11.3 Gosalakkal JA. Intracranial arachnoid cysts in children: a review of pathogenesis, clinical features, and management. Pediatric neurology. 2002 Feb 1;26(2):93-8.
  12. ↑ 12.0 12.1 12.2 12.3 Logan C, Asadi H, Kok HK, Looby S, O’Hare A, Thornton J, Brennan P. Arachnoid cysts-common and uncommon clinical presentations and radiological features.
  13. ↑ 13.0 13.1 13.2 13.3 Huang JH, Mei WZ, Chen Y, Chen JW, Lin ZX. Analysis on clinical characteristics of intracranial arachnoid cysts in 488 pediatric cases. International journal of clinical and experimental medicine. 2015;8(10):18343.
  14. ↑ Castle-Kirszbaum MD, Uren B, King J, Wang YY, Goldschlager T. Glimpse into pathophysiology of sellar arachnoid cysts. World Neurosurgery. 2018 Nov 1;119:381-3.
  15. ↑ Qi W, Zhao L, Fang J, Chang X, Xu Y. Clinical characteristics and treatment strategies for idiopathic spinal extradural arachnoid cysts: a single-center experience. Acta neurochirurgica. 2015 Mar;157:539-45.
  16. ↑ Kramer U, Nevo Y, Reider-Groswasser I, Sheuer E, Meyer JJ, Leitner Y, Phatal A, Harel S. Neuroimaging of children with partial seizures. Seizure. 1998 Apr 1;7(2):115-8.
  17. ↑ Heier LA, Zimmerman RD, Amster JL, Gandy SE, Deck MD. Magnetic resonance imaging of arachnoid cysts. Clinical imaging. 1989 Dec 1;13(4):281-91.
  18. ↑ Karnazes AC, Kei J, Le MV. Image diagnosis: arachnoid cyst. The Permanente Journal. 2015;19(2):e110.
  19. ↑ Hong S, Pae J, Ko HS. Fetal arachnoid cyst: characteristics, management in pregnancy, and neurodevelopmental outcomes. Obstetrics & Gynecology Science. 2023 Jan 31;66(2):49-57.
  20. ↑ Hapsari P, Celia, Nagpal C, Andre, Ronny, Shen R. Epilepsy-associated open-lip schizencephaly with arachnoid cyst: a rare case report. The Egyptian Journal of Neurology, Psychiatry and Neurosurgery. 2023 Feb 15;59(1):23.
  21. ↑ Schmutzer-Sondergeld M, Gencer A, Niedermeyer S, Quach S, Stoecklein VM, Teske N, Schichor C, Terpolilli NA, Kunz M, Thon N. Evaluation of surgical treatment strategies and outcome for cerebral arachnoid cysts in children and adults. Acta Neurochirurgica. 2024 Jan 27;166(1):39.
  22. ↑ Couvreur T, Hallaert G, Van Der Heggen T, Baert E, Dewaele F, Okito JP, Vanhauwaert D, Deruytter M, Van Roost D, Caemaert J. Endoscopic treatment of temporal arachnoid cysts in 34 patients. World neurosurgery. 2015 Sep 1;84(3):734-40.
  23. ↑ Choi JU, Kim DS, Huh R. Endoscopic approach to arachnoid cyst. Child's Nervous System. 1999 Jul;15:285-91.
  24. ↑ Oertel JM, Wagner W, Mondorf Y, Baldauf J, Schroeder HW, Gaab MR. Endoscopic treatment of arachnoid cysts: a detailed account of surgical techniques and results. Neurosurgery. 2010 Sep 1;67(3):824-36.
  25. ↑ Sinurat R. Severe headache and seizure free after microscopic fenestration craniotomy of middle Fossa arachnoid cyst: Case series. International Journal of Surgery Case Reports. 2022 May 1;94:107101.
  26. ↑ Dlaka D, Raguž M, Muller D, Romić D, Almahariq F, Dlaka J, Kaštelančić A, Chudy D. Intraparenchymal supratentorial arachnoid cyst: a case report. Egyptian Journal of Neurosurgery. 2019 Dec;34:1-6.
  27. ↑ Thompson D. Hydrocephalus and shunts. In Neurosurgery: Principles and Practice 2005 Jan 4 (pp. 425-442). London: Springer London.
  28. ↑ Rigante L, Borghei-Razavi H, Recinos PF, Roser F. An overview of endoscopy in neurologic surgery. Cleveland Clin. J. Med.. 2019 Oct 1;86(10).
  29. ↑ Poologaindran A, Profyris C, Young IM, Dadario NB, Ahsan SA, Chendeb K, Briggs RG, Teo C, Romero-Garcia R, Suckling J, Sughrue ME. Interventional neurorehabilitation for promoting functional recovery post-craniotomy: a proof-of-concept. Scientific reports. 2022 Feb 23;12(1):3039.
  30. ↑ King LA, Horak FB, Mancini M, Pierce D, Priest KC, Chesnutt J, et al. Instrumenting the balance error scoring system for use with patients reporting persistent balance problems after mild traumatic brain injury. Arch Phys Med Rehabil (2014) 95(2):353–9.10.1016/j.apmr.2013.10.015
  31. ↑ Ben M, Glinsky JV, Chu J, Spooren AI, Roberts S, Chen LW, Denis S, Lorusso M, Jorgensen V, Gollan EJ, Agostinello J. Early and intensive Motor Training for people with spinal cord injuries (the SCI-MT Trial): description of the intervention. Spinal Cord. 2023 Nov;61(11):600-7.
  32. ↑ Hanssen B, Peeters N, De Beukelaer N, Vannerom A, Peeters L, Molenaers G, Van Campenhout A, Deschepper E, Van den Broeck C, Desloovere K. Progressive resistance training for children with cerebral palsy: A randomized controlled trial evaluating the effects on muscle strength and morphology. Frontiers in physiology. 2022 Oct 4;13:911162.
  33. ↑ Pritcher MR, Whitney SL, Marchetti GF, Furman JM. The influence of age and vestibular disorders on gaze stabilization: a pilot study. Otology & Neurotology. 2008 Oct 1;29(7):982-8.
  34. ↑ Chatchawan U, Thongbuang S, Yamauchi J. Characteristics and distributions of myofascial trigger points in individuals with chronic tension-type headaches. Journal of physical therapy science. 2019;31(4):306-9.
  35. ↑ Bini P, Hohenschurz-Schmidt D, Masullo V, Pitt D, Draper-Rodi J. The effectiveness of manual and exercise therapy on headache intensity and frequency among patients with cervicogenic headache: a systematic review and meta-analysis. Chiropractic & manual therapies. 2022 Nov 23;30(1):49.
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