Nontraumatic de novo arachnoid cyst

Nontraumatic de novo arachnoid cyst

Intracranial de novo arachnoid cysts in adults are very rare, suggesting the involvement of head trauma and inflammatory diseases.

Benign extracerebral fluid collections in infancy may constitute a significant risk factor for development of de novo arachnoid cysts. These findings support a 2-hit hypothesis for the development of arachnoid cysts, in which the combination of an embryological defect in arachnoid development followed by a second event leading to impairment of CSF fluid absorption in early childhood could lead to abnormal CSF dynamics and the consequent expansion of fluid collections in the intraarachnoid spaces 1).

Case reports

Yokoyama et al., reported a symptomatic adult case of nontraumatic de novo arachnoid cyst on the ventral medulla oblongata.

A 56-year-old man came to the hospital complaining of dysphagia and writing difficult since 3 months ago. There was no history of head injury or inflammatory disease. A 25-mm cystic lesion was found on the ventral side of the medulla oblongata on brain MRI, and the lower cranial nerve and medulla oblongata were highly compressed. The lesion did not exist on MRI performed 9 years ago. Capsular resection was performed and the histological diagnosis was a typical arachnoid cyst. After the operation, all neurological symptoms disappeared, and no recurrence has been observed after 6 months.

The pathophysiology of nontraumatic de novo arachnoid cysts has many unknown features, and it appears necessary to accumulate further case reports 2).

A 71-year-old male patient with progressive vertigo who had previous brain magnetic resonance imaging studies without abnormalities. Another MRI was performed 3 years from the last study that showed interval development of a large cystic lesion compressing the right cervicomedullary junction, as well as radiologic evidence of neurosarcoidosis. Intraoperative findings showed a cystic mass with clear, gelatinous fluid. The cyst was drained, and the walls were resected and sent to pathology. Histopathologic testing confirmed the lesion was an arachnoid cyst. The patient’s vertiginous symptoms improved after surgery.

This case represents the first incidence of a pathology-proven, nontraumatic de novo arachnoid cyst 3).



Mattei TA, Bond BJ, Sambhara D, Goulart CR, Lin JJ. Benign extracerebral fluid collection in infancy as a risk factor for the development of de novo intracranial arachnoid cysts. J Neurosurg Pediatr. 2013 Dec;12(6):555-64. doi: 10.3171/2013.8.PEDS1399. Epub 2013 Oct 4. PubMed PMID: 24093592.

Yokoyama K, Sugie A, Yamada M, Tanaka H, Ito Y, Yamashita M, Kawanishi M. Formation of de Novo Symptomatic Premedullary Arachnoid Cyst in Adult. World Neurosurg. 2019 Jul 10. pii: S1878-8750(19)31935-7. doi: 10.1016/j.wneu.2019.07.029. [Epub ahead of print] PubMed PMID: 31301440.

Clifton W, Rahmathulla G, Tavanaiepour K, Alcindor D, Jakubek G, Tavanaiepour D. Surgically Treated de Novo Cervicomedullary Arachnoid Cyst in Symptomatic Adult Patient. World Neurosurg. 2018 Aug;116:329-332. doi: 10.1016/j.wneu.2018.05.046. Epub 2018 May 16. PubMed PMID: 29777892.

Arachnoid granulation

Arachnoid granulation

Arachnoid granulations (or arachnoid villi) are small protrusions of the arachnoidthrough the dura mater.

Largest granulations lie along the superior sagittal sinus.

They are, however, present along other dural sinuses as well. Smaller granulations are called villi, large calcified ones are referred to as pacchionian body.


They allow cerebrospinal fluid (CSF) to exit the subarachnoid space and enter the blood stream.

The diffusion across the arachnoid granulations into the superior sagittal sinus returns CSF to the venous circulation.

They act as one-way valves. Normally the pressure of the CSF is higher than that of the venous system, so CSF flows through the villi and granulations into the blood. If the pressure is reversed for some reason, fluid will not pass back into the subarachnoid space. The reason for this is not known. It has been suggested that the endothelial cells of the venous sinus create vacuoles of CSF, which move through the cell and out into the blood.

The importance of arachnoid granulations for the drainage of CSF is controversial. By some accounts, a large portion (perhaps the majority) of CSF is drained through lymphatics associated with extracranial segments of the cranial nerves. A large proportion of CSF is believed to leave the cranial vault through the axons of CN I (olfactory nerve) through their extension through the cribriform plate.

On the inner surface of cranial bones, small pits called granular fovea are produced by arachnoid granulations.

History and etymology

Arachnoid granulations (older terms: Pacchioni’s granulation (after Italian anatomist Antonio Pacchioni) or pacchionian body) resorb CSF into vascular system and occasionally cause a bony radiolucency, usually near the superior sagittal sinus.


They increase in size and number with age and are seen in approximately two-thirds of patients. They are most commonly seen at the junction between the middle and lateral thirds of the transverse sinuses near the entry sites of the superficial veins.


Arachnoid granulations (AG) are composed of dense, collagenous connective tissue that includes clusters of arachnoid cells.


They most frequently occur in a parasagittal location with the transverse and superior sagittal sinuses being the most common locations. The granulations typically occur next to the entrance of a superficial draining cortical vein into a sinus (similiar to colonic diverticuli occuring next to penetrating vessels).

Clinical features

Although usually incidental, giant arachnoid granulations that are of sufficient size to fill the lumen of a dural sinus and cause local dilation or filling defects can rarely cause symptoms due to sinus obstruction leading to venous hypertension.

Rodrigues and Santos reported a rare case of a brain herniation into a giant arachnoid granulation in an asymptomatic elderly male patient, which was discovered incidentally 1).

Kan et al., reported a 31-year-old man presented with a 3-month history of progressive bifrontal headaches and a giant arachnoid granulation at the posterior superior sagittal sinus. Intrasinus pressure measurements showed no significant pressure difference across the lesion to explain the headaches, which were then treated medically. Dural sinus pressure measurement, in certain cases of giant arachnoid granulations, can be used to exclude the lesion as the cause of the patient’s symptoms 2).


They are often discovered as incidental findings in the transverse and posterior superior sagittal sinus 3) 4) 5).

They appear osteolytic, sharply circumscribed indolent-appearing lucencies on skull CT or x-rays, or a filling defect in dural venous sinuses, which can be mistaken for Dural venous sinus thrombosis.


The granulations are typically of CSF density and protrude into the calvaria or a dural venous sinus causing a filling defect. They may simulate a dural venous sinus thrombosis but are usually easy differentiated given their round well-defined shape and classic location.


Signal characteristics are generally those of CSF 6):

T1: low signal intensity

T2: high signal intensity; iso- or even slightly hyperintense to CSF

FLAIR: should attenuate

T1 C+ (Gd): no enhancement

Giant granulations (>10 mm) may show atypical MRI signal characteristics, with higher T1 and T2 signal than CSF and incomplete FLAIR signal suppression 7). Rarely these may cause sinus obstruction 8).

Differential diagnosis

1.- Extradural mass.

Unicameral bone cysts (UBC), also known as simple bone cysts, are common benign bone lesions filled with fluid, primarily occurring in children and adolescents. Although they can develop in any bone, UBCs usually affect the long bones.

A 53 year old male patient was found incidentally to have a calvarian lesion in the parietal region overlying the superior sagittal sinus (SSS). The differential diagnosis included a large arachnoid granulation, haemangioma of bone, a giant cell tumour or tuberculous infection. The patient was planned for elective surgery to remove the lesion and establish the diagnosis. Surgery was uneventful.

This is the first case of UBC affecting the cranial vault. The patient underwent surgery 9).

2.- Dural venous sinus thrombosis.

MR imaging combined with MR venography is the most useful diagnostic tool to differentiate 10).

The differential diagnosis with thrombosis or intrasinusal tumoral lesions can easily made on the basis of three typical radiological features of the granulations: the hyperintensity of the lesions on FLAIR, a blood vessel within the lesion and bone erosion 11).

Case reports

A 6-year-old girl complained of diplopia and headache over a 2-week period after sustaining a minor head injury. Her neurological examinations were normal, but visual examination identified bilateral papilledema. Magnetic resonance imaging of the brain revealed a protruding nodular lesion causing compression within the anterior superior sagittal sinus in the midline, showing high signal intensity on T2-weighted imaging (T2WI) and low signal intensity on T1WI, similar to that of cerebrospinal fluid. Enhanced T1WI showed irregular narrowing of the anterior superior sagittal sinus adjacent to this lesion. The cortical vein drained to the frontal pole of the arachnoid granulation lesion and into the superior sagittal sinus. No other parenchymal abnormality was noted. A lumbar puncture showed increased opening pressure (30 mmHg), and the laboratory findings were normal. Based on the imaging and clinical findings, benign intracranial venous hypertension with giant arachnoid granulation was diagnosed. The patient’s symptoms were reduced satisfactorily following daily treatment with 750 mg acetazolamide 12).

A 45-year-old male patient which was associated with left temporal thrombosed dural arteriovenous fistula (AVF) whose thrombosed draining veins were seen converging towards the site of giant arachnoid granulation (GAG). The patient presented with three episodes of generalised tonic-clonic seizures and improved with conservative treatment. No reports of such association of GAG with AVF is available in the literature, and Karegowda et al., believe it could have occurred due to venous hypertension induced by GAG 13).

A child who presented with a mass within the superior sagittal sinus and an anomalous draining vein. Herein, the diagnosis of a giant AG was made. Clinicians who view or interpret imaging of the head should be aware of these anatomical variants and though when very large, apparently, do not necessarily result in pathology. Based on this case report, giant AG might also demonstrate anomalous draining veins 14).



Rodrigues JR, Santos GR. Brain Herniation into Giant Arachnoid Granulation: An Unusual Case. Case Rep Radiol. 2017;2017:8532074. doi: 10.1155/2017/8532074. Epub 2017 Mar 14. PubMed PMID: 28392955; PubMed Central PMCID: PMC5368369.
2) , 8)

Kan P, Stevens EA, Couldwell WT. Incidental giant arachnoid granulation. AJNR Am J Neuroradiol. 2006 Aug;27(7):1491-2. PubMed PMID: 16908565.

Chin SC, Chen CY, Lee CC, et al. Giant arachnoid granulation mimicking dural sinus thrombosis in a boy with headache: MRI. Neuroradiology 1998;40:181–83

Arjona A, Delgado F, Fernandez-Romero E. Intracranial hypertension secondary to giant arachnoid granulations. J Neurol Neurosurg Psychiatry 2003;74:418

Mamourian AC, Towfighi J. MR of giant arachnoid granulation: a normal variant presenting as a mass within the dural venous sinus. AJNR Am J Neuroradiol 1995;16:901–04

Ikushima I, Korogi Y, Makita O, Yamura M, Kawano H, Kohama M, Arikawa K, Takahashi M. MRI of arachnoid granulations within the dural sinuses using a FLAIR pulse sequence. Br J Radiol. 1999 Nov;72(863):1046-51. PubMed PMID: 10700819.

Trimble CR, Harnsberger HR, Castillo M, Brant-Zawadzki M, Osborn AG. “Giant” arachnoid granulations just like CSF?: NOT!! AJNR Am J Neuroradiol. 2010 Oct;31(9):1724-8. doi: 10.3174/ajnr.A2157. Epub 2010 Jun 25. PubMed PMID: 20581064.

Eristavi A, Sabin I, Al-Sarraj S, Aizpurua M. Cranial vault unicameral bone cyst. Br J Neurosurg. 2019 Jan 29:1-2. doi: 10.1080/02688697.2018.1519113. [Epub ahead of print] PubMed PMID: 30691312.

Ayaz E, Atalay B, Baysal B, Senturk S, Aslan A. Giant arachnoid granulation mimicking dural sinus thrombosis. North Clin Istanb. 2017 Aug 26;4(2):185-187. doi: 10.14744/nci.2017.93063. eCollection 2017. PubMed PMID: 28971178; PubMed Central PMCID: PMC5613268.

De Keyzer B, Bamps S, Van Calenbergh F, Demaerel P, Wilms G. Giant arachnoid granulations mimicking pathology. A report of three cases. Neuroradiol J. 2014 Jun;27(3):316-21. doi: 10.15274/NRJ-2014-10047. Epub 2014 Jun 17. PubMed PMID: 24976198; PubMed Central PMCID: PMC4202885.

Park H, Lim GY, Eom TH. Giant arachnoid granulation in a child with benign intracranial hypertension: an unusual case. Childs Nerv Syst. 2018 Dec;34(12):2525-2527. doi: 10.1007/s00381-018-3898-3. Epub 2018 Jul 17. PubMed PMID: 30019113.

Karegowda LH, Rajagopal K, Krishnamurthy SK, Lakshmana S. Giant arachnoid granulation with a thrombosed dural arteriovenous fistula. BMJ Case Rep. 2018 Jun 27;2018. pii: bcr-2018-224851. doi: 10.1136/bcr-2018-224851. PubMed PMID: 29950364.

Umeh R, Oskouian RJ, Loukas M, Tubbs RS. Giant Arachnoid Granulation Associated with Anomalous Draining Vein: A Case Report. Cureus. 2017 Mar 1;9(3):e1065. doi: 10.7759/cureus.1065. PubMed PMID: 28409066; PubMed Central PMCID: PMC5375954.

Cerebellopontine angle arachnoid cyst

Cerebellopontine angle arachnoid cyst


Middle cranial fossa is the most common site of intracranial arachnoid cysts, followed by the cerebellopontine angle (CPA) and suprasellar area.

Gardner et al., in 1960 attributed a embryonal atresia of the fourth ventricle as the cause of “arachnoid cyst” of the cerebellopontine angle 1).

Clinical features

They usually remain asymptomatic so they are often diagnosed incidentally during radiological evaluation for other reason 2).

As these cysts enlarge, they may compress surrounding structures and cause neurological symptoms. Patients may present with vague, nonspecific symptoms such as headache and ataxia. 3).

These cysts also can cause dysfunction of specific cranial nerves, including III, IV, VI (to cause diplopia), V (to induce trigeminal neuralgia), VII (to cause congenital or acquired facial paralysis), VIII (to cause hearing loss, tinnitus, vertigo), X (to result in hoarseness and dysphagia) 4) 5) 6).

Gurkas et al. report a patient with cranial nerve palsies and mirror movements found in upper extremities. They postulated that CPA arachnoid cyst compressing the brain stem and the pyramidal decussation may lead to mirror movements 7).


MRI (magnetic resonance imaging) scan techniques have led to CPA arachnoid cysts being more frequently diagnosed and with a higher degree of certainty. The need for further understanding of their natural history as well as for the development of a management rationale has been highlighted with this increased rate of diagnosis.

In the series of Alaani et al. these lesions have a characteristic location in the posterior-inferior aspect of the CPA below the facial and vestibulocochlear nerves. These cysts did not show change in size on repeated MRI scan and the patients’ symptoms did not progress over the period of follow up 8).

Differential diagnosis

A cerebellopontine angle lesion could be a vestibular schwannoma, meningioma, epidermoid cyst, or less likely, arachnoid cyst, metastasis, lower cranial nerves schwannoma, lipoma, hemangioma, paraganglioma, or vertebra-basilar dolichoectasia. Primary meningeal melanocytoma is a rare neoplasm, especially when it occurs at the cerebellopontine angle 9).

MRI is helpful in differentiating arachnoid cysts from those cystic lesions. If a pathologic cause of a retrocochlear disorder is suspected in a patient with a unilateral sensorineural hearing loss and tinnitus, MRI should be performed to evaluate the cerebellopontine angle.

On MRI, arachnoid cysts appear as smooth-surfaced lesions that in all magnetic resonance sequences exhibit a signal characteristic of CSF. In contrast, epidermoid cysts show mixed signals on FLAIR images and high signals on diffusion weighted images. Neurenteric cysts present high signals on T1-weighted images and cystic schwannomas show some foci of contrast enhancement on T1-weighted postcontrast images 10) 11).

The rising of a neuroglial cyst from the nerve sheath is a finding that brings other possible origins of neuroglial cysts into consideration 12).


The optimal surgical management of arachnoid cysts remains controversial.

Although surgery for these entities is controversial, arachnoid cysts can be treated surgically with open craniotomy for cyst removal, fenestration into adjacent arachnoid spaces, shunting of cyst contents, or endoscopic fenestration.

Alaani et al. support a conservative management approach to the majority of these cysts 13).

The definitive treatment for these arachnoid cysts is a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls 14).


The risks of surgery are few, but complications (meningitis, hemiparesis, oculomotor palsy, subdural hematoma, grand mal epilepsy, and death) have been reported 15). 16) 17).

Olaya et al. report the first case of complete recovery from sensorineural hearing loss and facial weakness following endoscopic fenestration 18).

Case series

3 pediatric patients with CPA arachnoid cysts (2 with hearing loss and 1 with recurrent headaches) who underwent neurosurgical treatment at the authors’ institution.

Four pediatric patients were diagnosed with CPA arachnoid cysts at the International Neuroscience Institute during the period from October 2004 through August 2012, and 3 of these patients underwent surgical treatment. The authors describe the patients’ clinical symptoms, the surgical approach, and the results on long-term follow-up. RESULTS One patient (age 14 years) who presented with headache (without hearing deficit) became asymptomatic after surgical treatment. The other 2 patients who underwent surgical treatment both had hearing loss. One of these children (age 9 years) had recent-onset hypacusia and experienced complete recovery immediately after the surgery. The other (age 6 years) had a longer history (2 years) of progressive hearing loss and showed an interruption of the deficit progression and only mild improvement at the follow-up visit.

CPA arachnoid cysts are uncommon in pediatric patients. The indication and timing of the surgical treatment are fundamental, especially when a hearing deficit is present 19)


Alaani et al. present a series of five adult patients with different clinical presentations attributed to CPA arachnoid cysts. These lesions have a characteristic location in the posterior-inferior aspect of the CPA below the facial and vestibulocochlear nerves. These cysts did not show change in size on repeated MRI scan and the patients’ symptoms did not progress over the period of follow up. The findings would support a conservative management approach to the majority of these cysts 20).


Five patients (three male and two female patients) with a mean age of 5.6 years have been operated on at the Department of Neurosurgery, New York University Medical Center, USA. since 1980 till 1997.

All five arachnoid cysts compressed the cerebellum or brain stem. One patient had associated hydrocephalus. Three patients presented with refractory headaches associated with nausea and vomiting. The remaining two patients presented with cerebellar signs. No patient had an initial cranial neuropathy.

All patients underwent a retrosigmoid suboccipital craniotomy and microsurgical resection and fenestration of the cyst walls. One patient underwent two procedures. A cystoperitoneal shunt was inserted at the first operation. After the shunting procedure, the patient’s condition deteriorated; however, after the microsurgical resection and fenestration, his symptoms improved. With a mean 5.2-year follow-up, there has been no evidence of clinical or radiographic recurrence 21).


Two cases of arachnoid cysts of the cerebello-pontine angle. The otologic symptoms were unsteadiness, hearing fall and tinnitus. In the first case, the patient who presented a cerebellar syndrome was operated. Afterwards the hearing felt and he developed a transient hydrocephalus. The symptoms disappeared in 9 months. In the second cas, the patient was not operated. She was treated medically and supervised. Then the symptoms disappeared too. The authors review the paraclinic exams especially MR, relevant to the diagnosis and discuss the opportunity of a surgical operation 22).


Ten cases of arachnoid cysts of the ponto-cerebellar angle are presented. In most cases, local arachnoiditis is disclosed during surgery, directing the discussion toward acquired pathology, and perhaps toward local infection. The clinical symptoms are dominated by the cochleo-vestibular deficit, but the involvement of the V and the VII cranial nerves is inconstant and discreet. At the present time, C.T. scan allows a rapid diagnosis but the prognosis must be reserved, in account to the possibility of a local post operatory arachnoiditis 23).

Case reports


A 4-year-old boy with global developmental delay, esotropia, moderate aortic root dilation, genu valgum, and in-toeing gait. MRI brain for evaluation of neonatal hypotonia revealed a left cerebellopontine angle arachnoid cyst. He referred on newborn hearing screening, and diagnostic auditory brainstem response (ABR) showed left profound retrocochlear hearing loss. Surgical intervention for the arachnoid cyst was deferred, with spontaneous resolution at age two years without hearing recovery. CMA revealed a novel, de novo 5.1 Mb microdeletion of 22q13.31q13.33 not involving SHANK3, a gene typically deleted in PMS.

As diagnostic sensitivity improves, smaller chromosomal imbalances will be detectable related to milder or different phenotypes. They present two patients with novel deletions of chromosome 22q13 associated with multiple congenital anomalies and features distinct from PMS 24).


A 14-year-old previously healthy girl presented to our outpatient clinic with a 6-weeks history of frontal headache. They typically would start in the occipital region and then radiate bifrontally. The neurological examination was unremarkable. Magnetic resonance imaging revealed an extra-axial bilateral lesion in bilateral cerebellopontine angle, larger on left side. The lesions were homogeneously hypointenese on T1-weighted imaging and hyperintense on T2-weighted imaging without evidence of contrast enhancement and without evidence of restriction on diffusion-weighted imaging. No surgical treatment was indicated.

Bilateral arachnoid cysts of the cerebellopontine angle are very infrequent and the main indication for surgery is the existence of clinical symptoms or neurological deficit coincident with the locations of the cysts 25).


Petscavage et al. present the case of a 49-year-old woman who presented with acute, nonprogressive left sensorineural hearing loss and benign positional vertigo that was associated with an arachnoid cyst of the cerebellopontine angle. The presence of the lesion was documented by MRI examinations that were obtained 7 years apart. Arachnoid cysts at the cerebellopontine angle are usually found incidentally on MRI performed for unrelated reasons. However, if the arachnoid cyst displaces or compresses adjacent cranial nerves, symptoms may result. They review the salient imaging features of arachnoid cysts that allow their differentiation from other lesions of the cerebellopontine angle 26).

Gurkas et al. report a patient with a CPA arachnoid cyst. He presented with cranial nerve palsies and mirror movements found in upper extremities. They postulated that CPA arachnoid cyst compressing the brain stem and the pyramidal decussation may lead to mirror movements, and conclude that mirror movements can be associated with CPA arachnoid cyst 27).

A 71-year old woman presenting with a right hemifacial spasm and an ipsilateral arachnoid cyst. Preoperative magnetic resonance imaging findings suggested a neurovascular compression caused by displacement of the facial-acoustic complex and the anterior inferior cerebellar artery by the cyst. Cyst excision and microvascular decompression of the facial nerve achieved permanent relief. The existing cases of arachnoid cysts causing hemifacial spasm are reviewed and the importance of a secondary neurovascular conflict identification and decompression in these cases is highlighted 28).

Trigeminal Neuralgia in a Child With a Cerebellopontine Angle Arachnoid Cyst 29).

Sharma et al. report two cases of bilateral CPA AC with their pathophysiology and review of literature 30).


Visagan et al. first report a CPA arachnoid cyst causing TGN in a paediatric case 31).


A 62-year-old man complaining of vertigo and progressive hearing loss was diagnosed with an arachnoid cyst at the right cerebellopontine angle based on magnetic resonance imaging (MRI). In this case-report, we used computed tomography (CT) cisternography to determine whether the arachnoid cyst communicated with the cerebrospinal fluid (CSF) space. Differentiating between a noncommunicating and communicating arachnoid cyst is required for presurgical evaluation. CT cisternography is a less used but reliable radiological technique for determining the presence of communication, and could therefore be included in the diagnostic work-up of arachnoid cysts. The patient underwent surgery with fenestration of the arachnoid cyst; his vertigo improved and his hearing was preserved 32).

Superior oblique myokymia (SOM) is a rare disorder with an unclear pathogenesis. We describe a first reported case of chronic disabling SOM in association with a cerebellopontine angle arachnoid cyst, who had a gradual and eventually complete symptomatic resolution 8 months following cyst marsupialisation. Among other aetiologies, SOM may therefore be due to abnormal CSF flow dynamics resulting in structural compromise of the nerve 33).


A 7-month-old infant presented to the hospital with a history of delayed milestones and an abnormal increase in head circumference. Magnetic resonance images and CT scans of the brain showed a large CSF cavity involving the entire brainstem and a right CPA arachnoid cyst causing obstruction of the fourth ventricle and dilation of the lateral and third ventricles. Cerebrospinal fluid diversion was performed by direct communication from the syringobulbia cavity to the left lateral ventricle and from the left lateral ventricle through another ventricular catheter; external ventricular drainage was performed temporarily for 5 days. Communication between the syrinx and arachnoid cyst was confirmed. Clinically, there was a reduction in head circumference, and serial MR imaging of the brain showed a decrease in the size of the syrinx cavity and the ventricle along with opening of the normal CSF pathways. The postoperative course was uneventful, and no further intervention was necessary. On follow-up of the child at 3 years, his developmental milestones were normal. Surgical intervention for this condition is mandatory. The appropriate type of surgery should be performed on the basis of the pathophysiology of the developing syringobulbia 34).

A 47-year-old woman complaining of sharp and lancinating pain in the right periauricular and submandibular areas visited our hospital. Swallowing, chewing, and lying on her right side triggered the pain. Her neurologic examination revealed no specific abnormalities. The results of routine hematologic and blood chemistry studies were all within normal limits. Carbamazepine and gabapentin were given, but her symptoms persisted. Her pain was temporarily relieved only by narcotic pain medication. MRI showed an arachnoid cyst located in the right cerebellomedullary cistern extending to the cerebellopontine cistern. Cyst removal was performed via a right retrosigmoid approach. Lateral suboccipital craniotomy was performed using the right park-bench position. After opening the dura and cerebellopontine angle, the arachnoid cyst was exposed. The arachnoid cyst was compressing the flattened lower cranial nerves at the right jugular fossa. Her symptoms resolved postoperatively. Two months after the operation, she was completely free from her previous symptoms 35).


A rare case of cerebellopontine angle arachnoid cyst manifesting as hemifacial spasm (HFS) is reported. The patient is a 42-year-old woman with 10-month history of left HFS. A preoperative magnetic resonance imaging scan showed a well-demarcated area, hypointense on T1-weighted imaging and hyperintense on T2-weighted imaging, in the left cerebellopontine angle, without contrast enhancement, resembling an arachnoid cyst. METHODS: The cyst was excised with microneurosurgical technique and the facial, vestibular, and acoustic nerves were completely decompressed from the arachnoid wall. RESULTS: The postoperative course was uneventful, and the left HFS disappeared immediately. Histologically, the cyst wall was a typical arachnoidal membrane. Ten months after surgery, the patient is symptom free. CONCLUSION: It is well-known that in approximately 10% of cases, trigeminal neuralgia can be caused by a space-occupying mass. However, the fact that HFS can also be caused by organic lesions as well as neurovascular compression is less well-known. Although the occurrence of tumor compression causing HFS has been previously recognized, cerebellopontine angle cysts have very rarely been described. The observation of a patient with a cerebellopontine angle arachnoid cyst causing HFS prompted us to review the literature relative to HFS caused by an organic lesion rather than neurovascular compression 36).


a patient with a CPA arachnoid cyst who presented with hoarseness (unilateral vocal cord paralysis) and dysphagia secondary to isolated compression of the vagus nerve. This rare presentation of a CPA arachnoid cyst has not been reported previously. CLINICAL PRESENTATION: The patient described is a 50-year-old man who experienced a precipitous onset of hoarseness and dsyphagia. An otolaryngological evaluation revealed right-sided vocal cord paralysis. Brain magnetic resonance images displayed a cystic mass at the right CPA and anterior displacement of the vagus nerve. INTERVENTION: The patient underwent retrosigmoidal craniectomy with cyst fenestration, which was well tolerated. Intraoperatively, Cranial Nerve X was found splayed over the cyst and was consequently decompressed. CONCLUSION: Postoperatively, the patient’s dysphagia completely resolved. However, the results of a laryngeal electromyocardiogram revealed minimal evidence of recovery in the affected vocal fold, and the patient continued to suffer from dysphonia. Although CPA arachnoid cysts are rare, they should be considered when a patient presents with an isolated cranial nerve palsy. Treatment options include cyst fenestration and cranial nerve decompression 37).


A 51 years old female is reported who was diagnosed by IRM of a 4,5 x 2 cm arachnoid cyst, situated on the left cerebello-pontine angle, with tinnitus, hearing loss and vertigo that mimicked a Meniere’s attack. We think thees benign tumors must be included in the differential diagnosis of Meniere’s disease because they can be indistinguishable from it clinically 38).


Higashi et al., reported the first case of hemifacial spasm with an ipsilateral cerebellopontine angle arachnoid cyst in a 25-year-old man. The patient underwent evacuation of the arachnoid cyst by a partial membranectomy without any beneficial effect, and finally got rid of the hemifacial spasm by reexploration and microvascular decompression of the facial nerve. The operative findings and results revealed that the cyst produced deviation of the ipsilateral posterior inferior cerebellar artery, which was secondarily in contact with the root exit zone of the facial nerve 39).

A 17-month-old girl who developed two cerebellopontine angle arachnoid cysts after posterior fossa surgery for a brain tumor. After surgical excision of the tumor the child developed a left cerebellopontine angle cyst. This was treated through a suboccipital craniectomy by evacuating the cyst and excising the cyst wall. Two months later the child developed a second right-sided cerebellopontine angle cyst. It was treated by inserting a cystoperitoneal shunt. This article presents the case with radiological evidence of the acquired nature of the cysts. It also includes a brief review of the clinical presentation, pathogenesis, radiological evaluation, and surgical treatment of arachnoid cysts with emphasis on those occurring in the posterior fossa 40).


A case of an arachnoid cyst in the cerebellopontine angle manifesting as contralateral trigeminal neuralgia is presented. Decompression and excision of the lesion resulted in total relief of symptoms. The possible causes of contralateral trigeminal neuralgia are briefly reviewed, and the surgical treatment of this entity is discussed 41).


A case of a cerebellopontine angle arachnoid cyst spontaneously disappeared is reported. A 1-year-and-11-month old boy was suffered from sudden onset of left facial palsy. CT scan demonstrated dilatation of left internal auditory canal and a cystic lesion in the left cerebellopontine angle. Neurological examination disclosed only left facial palsy and left hearing loss. There was no signs and symptoms of increased intracranial pressure. He was followed up by CT scan. Repeated CT scan showed non-enhanced cystic lesion, the attenuation value of which was similar to that of cerebrospinal fluid. The cyst expanded gradually, and the brain stem was severely compressed. Then operation was planned under the diagnosis of left cerebellopontine angle arachnoid cyst about 2 years after the onset. But CT scan performed before operation showed disappearance of the cyst. Without operation the patient was followed by CT scan. There is no recurrence of the cyst. Natural history of arachnoid cyst will be well understood with repeated CT scan 42).



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