178 arachnoid cysts

Youmanns

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 Primary arachnoid 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 membranes of 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 R esult from abnormal 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 del ay

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 and sylvian 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 and sylvian fissure cysts Type II Larger triangular- or quadrangular-appearing  cysts I nvolve 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 M ore likely than type I cysts to require treatment

12. Middle fossa and sylvian 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.

13. Parasellar intra-arachnoid cysts Suprasellar c ommon, 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

14. Parasellar intra-arachnoid cysts Intrasellar u ncommon typically present in the fourth or fifth decade of life headache,visual abnormalities or endocrinopathy Ddx : craniopharyngioma or Rathke’s cleft cyst

15. Other type Arachnoid cysts 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

16. Other type Interhemispheric  cysts 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

17. 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

18. 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

19. Imaging CT sharply circumscribed, 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

20. Imaging MRI better detection 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 

21. Treatment alternative Conservative Surgery

22. Conservative asymptomatic patients middle fossa arachnoid cysts : Chronic subdural hemorrhage  surgery Single FU 6-8 wk for rule-out any change

23. Surgery Increased ICP or hydrocephalus Headache : most common in sylvian fissure arachnoid cysts

24. Surgery Craniotomy for Cyst 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

25. 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