Intracanalicular arachnoid cyst mimicking acoustic neuroma: CT and MRI

Non-schwannomatosis lesions of the internal acoustic meatus-a diagnostic challenge and management: a series report of nine cases

Vestibular schwannomas (VS) are the most common lesions of cerebellopontine angle (CPA) corresponding to 76-91 % of the cases. Usually, these lesions present typical CT and MRI findings. Non-schwannomatous tumors restricted to the internal auditory meatus (IAM) are rare and their preoperative radiological diagnosis may be difficult. This article describes nine surgically treated intrameatal non-schwannomatous lesions (NSL) and reviews the literature. In the last 16 years, a total of 471 patients with diagnosis of VS were operated on in our department. Preoperatively, 42 patients had diagnosis of intrameatal schwannomas, but surgery revealed in nine cases NSL (3 meningiomas, 3 arachnoiditis/neuritis, 1 cavernoma, 1 vascular loop, and 1 arachnoid cyst). Most frequent symptoms presented by patients with NSL were hearing loss 89 % (8/9) of patients, tinnitus 78 % (7/9), and vertigo 33 % (3/9). Almost all lesions (8/9) presented MRI findings of isointense signal in T1W with contrast enhancement. The only exception was the arachnoid cyst with intracystic bleeding, which was hyperintense in T1W that is not enhanced with contrast. This series shows an occurrence of 21.4 % of non-schwannomatous tumors in 42 cases of lesions restricted to the IAM. Whenever a solely intrameatal enhanced tumor is detected, it is necessary to think about other diagnostic possibilities rather than VS. Therapeutic management may be changed, specially if radiosurgical treatment is considered.

Cochlear Implantation in Extraordinary Cases

BACKGROUND

Although cochlear implantation has been almost a standard otological procedure worldwide, it may still create a dilemma for the surgeon in some unusual instances such as Seckel syndrome, aural atresia and posterior fossa arachnoid cyst.

CASE REPORT

Three extraordinary cases of cochlear implantation were reported. The first case was a case of Seckel syndrome with a cardiac pacemaker due to complete atrioventricular block. The second case had posterior fossa arachnoid cyst that had retrosigmoid cyst removal and cochlear implantation simultaneously. The last case had cochlear implantation in the ear with congenital aural atresia. All cases could be implanted successfully with full electrode insertion and good audiological outcome. Delayed facial paralysis that occurred in the patient with arachnoid cyst resolved spontaneously.

CONCLUSION

This study addressed the efficiency of cochlear implantation in cases of Seckel syndrome, complete atrioventricular block managed with cardiac pacemaker, congenital aural atresia and posterior fossa arachnoid cyst. In addition, the retrosigmoid approach and cochlear implantation can be performed simultaneously.

Arachnoid cysts confined to the internal auditory canal or facial nerve canal

OBJECTIVE

To illustrate the morphological characteristics and pathological significance of arachnoid cysts confined to the internal auditory canal or facial nerve canal.

DESIGN

Retrospective case series.

SUBJECTS

Three patients' cases were reviewed, and temporal bone sections examined histologically.

RESULTS

In this series, three intracanalicular arachnoid cysts were found in the internal auditory canal and one in the facial nerve canal. All lesions consisted of distinct, space-occupying cysts with a sharp boundary with surrounding tissues. They were thin-walled and compressed the surrounding nerve trunks to a variable degree. However, there was no indication that patients suffered meatal nerve dysfunction.

CONCLUSION

Arachnoid cysts can develop within the internal auditory canal or facial nerve canal. In our series, they were asymptomatic, which is quite different from most intracanalicular arachnoid cysts encountered in clinical practice.

Association of heterotopic neuroglial tissue with an arachnoid cyst in the internal auditory canal

An arachnoid cyst arising within the internal auditory canal, or within the cerebellopontine angle and subsequently extending into the internal meatus and enlarging it, is a rare occurrence. Nevertheless, the neurootologist and the neurosurgeon have an interest in its existence because its clinical manifestations are identical with the ones produced by a schwannoma, involving overwhelmingly the cochleovestibular nerve in that region. An equally rare observation in that location is the presence of ectopic neuroglial tissue. The two can occur independently or in combination. Examples of such lesions are presented, and their possible pathogenesis is discussed.

Foramen magnum arachnoid cyst induces compression of the spinal cord and syringomyelia: case report and literature review

It is very rare that a foramen magnum arachnoid cyst induces compression of the spinal cord and syringomyelia, and currently there are few treatment experiences available. Here we reported the case of a 43-year-old male patient who admitted to the hospital due to weakness and numbness of all 4 limbs, with difficulty in urination and bowel movement. MRI revealed a foramen magnum arachnoid cyst with associated syringomyelia. Posterior fossa decompression and arachnoid cyst excision were performed. Decompression was fully undertaken during surgery; however, only the posterior wall of the arachnoid cyst was excised, because it was almost impossible to remove the whole arachnoid cyst due to toughness of the cyst and tight adhesion to the spinal cord. Three months after the surgery, MRI showed a reduction in the size of the arachnoid cyst but syrinx still remained. Despite this, the symptoms of the patient were obviously improved compared to before surgery. Thus, for the treatment of foramen magnum arachnoid cyst with compression of the spinal cord and syringomyelia, if the arachnoid cyst could not be completely excised, excision should be performed as much as possible with complete decompression of the posterior fossa, which could result in a satisfying outcome.

Arachnoid Cyst Confined to the Internal Auditory Canal—Endoscope-Assisted Resection: Case Report and Review of the Literature

BACKGROUND AND IMPORTANCE:

An arachnoid cyst confined to the internal auditory canal is a rare condition. Different pathogeneses are discussed, and a progressive enlargement of the cysts has been reported. This case illustrates the beneficial aspect of endoscopic assistance in microsurgical resection of this lesion.

CLINICAL PRESENTATION:

A slowly progressive hearing loss developed in a 35-year-old woman over 2 years; she reported experiencing tinnitus for 7 years. Magnetic resonance imaging revealed a cystic lesion in the internal auditory canal appearing hypointense on T1-weighted images and hyperintense on T2-weighted images, suggesting an arachnoid cyst.

INTERVENTION:

The cyst wall was fenestrated and partially resected in an endoscope-assisted microsurgical technique. Adherent vestibular nerve fibers in the cyst wall prevented total removal of the cyst. The histological examination confirmed the diagnosis of an arachnoid cyst.

CONCLUSION:

The endoscope-assisted microsurgical technique enables a safe cyst resection with good visualization of important neurovascular structures within the internal auditory canal. Small remnants of the capsule that are firmly attached to important neurovascular structures should be left in place rather than risk neurological deficits.

Arachnoid cysts of the posterior fossa

BACKGROUND

The surgical indications and management of posterior fossa arachnoid cysts (AC) are still controversial. Different surgical techniques and management have already been suggested for arachnoid cysts of the posterior fossa. AC involving the posterior fossa and especially the cerebellopontine angle may carry a high surgical morbidity because of the involvement of important neurovascular structures (e.g., brain stem and cranial nerves). Only long-term follow-up will determine the best surgical technique for such lesions.

METHODS

Between 1990 and 1996 a total of 12 patients underwent surgery for arachnoid cysts involving the posterior fossa. In seven cases AC were located within the cerebellopontine angle (CPA), in three cases in the CPA with major extension dorsal to the brainstem, and in two cases at the CPA extending into the internal auditory canal.

RESULTS

A suboccipital retrosigmoid approach was performed in all patients. Radical resection of the cyst could be accomplished in all but one case. There was no mortality. Major postoperative morbidity was present in one case because of an intraoperative air embolism in the semisitting position and strong adherence of the cyst wall to the surrounding neurovascular structures. Long-term follow-up (mean, 3.3 years) revealed improvement of most preoperative symptoms.

CONCLUSION

Open surgery and radical removal of the AC located at the posterior fossa, based on our retrospective analysis, provide very good long-term postoperative results. The suboccipital approach provides a good and safe exposure of vascular structures and cranial nerves in the CPA and allows radical resection of the cyst, reducing the chance of recurrence.