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178 arachnoid cysts
This document discusses arachnoid cysts, which are benign, non-neoplastic lesions filled with cerebrospinal fluid. They are most commonly discovered in children and can cause headaches, seizures, and hydrocephalus depending on their location. Imaging such as CT and MRI is used to identify the cysts' location and communication with CSF spaces. Treatment options include conservative monitoring, surgery to fenestrate or excise the cyst, or shunt placement if associated with hydrocephalus.
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178 arachnoid cysts
- 1. Arachnoid Cysts 178 7/10/59 Nicholas M.Wetjen Marion L. Walker
- 2. Outline • Epidemiology • Pathology •Embryology • Clinical presentation • Imaging • Treatment alternative
- 3. Arachnoid Cysts • Benign •Non-neoplastic • Extra-axial • Intra-arachnoid lesions filled with fluid similar to or exactly like cerebrospinal fluid • 60% to 80% discovered in children • Male-to-female : 2 : 1
- 4. Arachnoid Cysts • Primaryarachnoid cysts • congenital cysts • loculated, compartmentalized, or freely communicating with the surrounding CSF cisterns • Secondary arachnoid cysts • result of another condition : meningitis, trauma, or hemorrhage • signs of previous inflammatory changes : gliosis or hemosiderin • cyst fluid may be xanthochromic, proteinaceous, or hemorrhagic
- 5. Epidemiology • 90 %supratentorial space
- 6. Pathology • Appearance • membranesof the cyst : delicate, filmy, translucent • islands of mesenchymal cells,meningoepithelial cell positive for epithelial membrane antigen(EMA) • underlying cortex is usually normal • distinguishing features of the arachnoid cyst wall versus a normal arachnoid membrane • split of the arachnoid layer at the margin of the cyst • the increased thickness of the collagen layer • the absence of the cobweb-like trabeculations of normal arachnoid
- 7. Embryology • Result fromabnormal embryologic development of the subarachnoid space • 15 weeks’ gestation • meninx primitiva, or perimedullary mesh : precursor to the pia mater and arachnoid • the rhombic roof ruptures, CSF pulses through this mesh, and the pia mater and arachnoid separate incompletely
- 8. Clinical Presentation • Headache: local mass effect • High intracranial pressure (ICP) • Hydrocephalus • Asymptomatic throughout life • Infants : macrocephaly, enlarged tense fontanelle, and splayed sutures with irritability, failure to thrive, and developmental delay
- 9. Supratentorial Arachnoid Cysts •Unilateral headache in the supraorbital or temporal region that may be exacerbated with physical exertion • Focal, complex-partial, or generalized seizures • Arachnoid cysts of middle fossa and sylvian fissure • Arachnoid cysts of parasellar intra-arachnoid • Arachnoid cysts of the cerebral convexities • Arachnoid cysts of the Interhemispheric • Arachnoid cysts in the quadrigeminal cistern
- 10. Middle fossa andsylvian fissure cysts • Type I • small, lenticular, biconvex collections • located at the anterior pole of the middle fossa directly posterior to the sphenoid ridge • communicate freely with the adjacent cisterns • little associated mass effect • do not have associated calvarial deformities • do not require treatment.
- 11. Middle fossa andsylvian fissure cysts • Type II • Larger triangular- or quadrangular-appearing cysts • Involve the proximal to mid aspect of the sylvian fissure with a medial border along the margin of the insula • They are less likely to communicate with adjacent basal cisterns with delayed contrast uptake on cisternography • More likely than type I cysts to require treatment
- 12. Middle fossa andsylvian fissure cysts • Type III • Large, rounded cysts that involve the entire length of the sylvian fissure • Marked mass effect and midline shift with thinning, scalloping, and expansion of the middle fossa cranial bones (thinning of temporal squama or displacement of the wings of the sphenoid bone) or splaying of cranial sutures in younger children. • They usually do not have communication with adjacent cisterns and often require surgical treatment.
- 14. Parasellar intra-arachnoid cysts •Suprasellar • common, almost exclusively in children • hydrocephalus by extending into the third ventricle and obstructing the aqueduct of Sylvius • visual abnormalities, including hemianopia or decline in acuity. Gait ataxia and opisthotonos • bobble-head doll syndrome • Endocrinopathy • Precocious puberty • growth hormone deficiency are the most common
- 15. Parasellar intra-arachnoid cysts •Intrasellar • uncommon • typically present in the fourth or fifth decade of life • headache,visual abnormalities or endocrinopathy • Ddx : craniopharyngioma or Rathke’s cleft cyst
- 16. Other type • Arachnoidcysts of the cerebral convexities • headaches or seizures • Arachnoid cysts in the quadrigeminal cistern • Hydrocephalus, Progressive macrocephaly • Parinaud’s syndrome, nystagmus, hearing deficits trochlear nerve palsy, and apneic spells
- 17. Other type • Interhemisphericcysts • often associated with agenesis of the corpus callosum • macrocephaly and asymmetric growth of the calvaria • increased ICP, developmental delay, • hypertonia or hypotonia, hemiparesis • ocular changes, and epilepsy
- 18. Infratentorial Arachnoid Cysts •tinnitus, vertigo, facial weakness, facial sensory loss, hearing loss, or ataxia • trigeminal neuralgia and hemifacial spasm • obstructive hydrocephalus • ataxia, nystagmus • cranial nerve dysfunction • progressive quadriparesis • Ddx : mega cisterna magna Dandy-Walker malformation epidermoid cyst, and large cystic tumors
- 19. Imaging • Plain radiographs •nonspecific thinning and deformity of the adjacent bone • Angiograms • show shifts of the adjacent vasculature and venous phase • Ultrasound • prenatal ultrasound has detected arachnoid cysts as early as 13 weeks’ gestation • sonolucent with enhanced transmission of the ultrasound beam through the collection and are thus hypoechogenic to surrounding brain
- 20. Imaging • CT • sharplycircumscribed, smoothly marginated lesions • arachnoid cyst walls are so thin that they are not visible on CT and not enhance, whereas the walls of cystic tumors may be visible • the fluid of an arachnoid cyst is identical to CSF • CT with intrathecal or intraventricular injection of metrizamide can simultaneously provide anatomic detail of the subarachnoid and intraventricular space • communicating arachnoid cysts : cyst fills with metrizamide, but the clearance of contrast from the cyst is delayed • noncommunicating cysts : no early entry of contrast into the cyst (2 to 6 hours), but contrast accumulates around the cyst
- 21. Imaging • MRI • betterdetection of smaller cysts and cysts adjacent to bony structures • DWI : differentiate epidermoids from arachnoid cysts • Electrocardiogram-gated cine-mode MRI sequences : demonstrate communication between intracranial arachnoid cyst and CSF spaces
- 22.
- 23. Conservative • asymptomatic patients •middle fossa arachnoid cysts : Chronic subdural hemorrhage surgery • Single FU 6-8 wk for rule-out any change
- 24. Surgery • Increased ICPor hydrocephalus • Headache : most common in sylvian fissure arachnoid cysts
- 25. Surgery • Craniotomy forCyst Excision and Fenestration • with or without marsupialization as the first-line approach • Shunt Placement • craniotomy and cyst fenestration subsequently required cystoperitoneal shunting for either cyst recurrence or no improvement in symptoms • patients with arachnoid cysts and associated hydrocephalus may require ventriculoperitoneal shunts in addition to cystoperitoneal shunts • ventricular decompression may increase the risk for subdural hematoma : High-pressure valves or flow-control valves to avoid drainage • Neuroendoscopic Management
- 27. Intraspinal Arachnoid Cysts •Congenital lesions • Associated with vertebral anomalies, neural tube defects, syringomyelia, and trauma • Most commonly thoracic • Compression of the spinal cord, nerve roots, or cauda equina and become symptomatic • Surgical decompression