Arachnoid cysts can occur at different intracranial sites, including the cerebellopontine angle (CPA). The incidence of arachnoid cysts is 1 per cent of all intracranial lesions. Recent advances in 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.

We 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. Our findings would support a conservative management approach to the majority of these cysts.

Difficult cerebellopontine angle (CPA) tumours namely large/giant vestibular schwannomas, vestibular schwannomas with a significant anterior extension and meningiomas of the posterior surface of the petrous bone extending anterior to the internal auditory canal (IAC) have always posed a problem for the otoneurosurgeon. Modifications of the enlarged translabyrinthine approach (ETLA) specifically aimed at dealing with these tumours are not reported. The aim of this paper is to introduce the transapical extension of ETLA which involves increased circumferential drilling around the IAC beyond 270°C. The extension allows enhanced surgical control over the tumour as well as the anterior aspect of the CPA including the prepontine cistern, the Vth and VIth cranial nerves. The extension is further classified into Type I and II depending upon the extent of drilling. Type I extension entails drilling around the IAC for 300–320° and is indicated for large/giant vestibular schwannomas (large vestibular schwannoma extrameatal diameter 3–3.9 cm, giant vestibular schwannoma extrameatal diameter [ges ]4 cm) and vestibular schwannomas with significant anterior extension. Type II extension involves complete drilling around the canal for 360° and is indicated for meningiomas of the posterior surface of the petrous bone extending anterior to the IAC.

Vestibular schwannomas are the most common tumours encountered in the cerebellopontine angle (CPA) region, accounting for 90 per cent of all lesions. Early pyogenic abscess following surgery and delayed abscesses due to retained foreign bodies have been reported. We describe a case of sterile abscess of unknown aetiology in the CPA region, occurring 13 years after surgical excision of a vestibular schwannoma. The clinical and radiological features were suggestive of recurrent vestibular schwannoma or malignant transformation.

We believe this is the first reported case of delayed occurrence of sterile abscess in the CPA region. Further the diagnostic difficulties of such rare lesions occurring in the CPA after vestibular schwannoma surgery are discussed.

Primary cerebellopontine angle (CPA) cholesteatoma grows slowly and silently in the subarachnoidal spaces. The diagnosis is often late, when the lesion has reached large dimensions. Surgical removal is the only available therapy. Fifteen consecutive cases of CPA cholesteatoma managed at a tertiary otoneurosurgical referral unit between September 1985 and April 1999 were reviewed. The study population, consisting of seven males and eight females, had a mean age of 44 years of age (range 21–69) at the time of surgery. The clinical, audiological and radiological presentations were examined. The tumours were classified according to the Moffat classification of CPA cholesteatomas. In 67 per cent of cases the presenting symptom was related to the vestibulo-cochlear nerve. The average duration of symptoms was 23 months (ranging from one month–10 years). The hearing preservation approaches were utilized the most (11 cases), while the translabyrinthine approach alone, or in association with a middle fossa craniotomy, was performed in four cases. Tumour removal was total in 12 cases and subtotal in three cases. In cases undergoing hearing preservation surgery the mean pre-operative pure tone average (PTA) for the frequencies 0.5, 1, 2, and 3 kHz was 19.3 dB HL (SD 13.84) and the mean pre-operative speech discrimination score (SDS) was 89.8 per cent (SD 5.97). In 44.4 per cent of patients the hearing was preserved and the mean post-operative PTA was 20.29 dB HL (SD 15.84). In five patients post-operative complications occurred. No peri- or post-operative death occurred in this series, one patient developed a recurrence 15 years after the initial surgery.

We report a case of a peripheral neuroectodermal tumour (pPNET) of the cerebellopontine angle of a 67-year-old woman. The patient’s age at presentation was highly unusual. This case highlights the difficulties encountered, both clinically and pathologically, in securing the correct diagnosis of such a rare condition presenting in this relatively inaccessible area. The development of the nomenclature and classification of neuroectodermal tumours is traced. Recent advances in immunohistochemistry and genetic typing have shown the close relationship between pPNET and the previously difficult to classify Ewing’s sarcoma and Askin’s tumour.

The otolaryngologist who requests magnetic resonance imaging (MRI) scans to exclude cerebellopontine angle (CPA) tumours may discover incidental pathologies. We retrospectively reviewed the results of 644 consecutive MRI screening scans with the aim of identifying findings other than CPA tumours. Two hundred and eighty-nine (45 per cent) scans featured one or more anomalies or abnormalities, including CPA tumour (23, four per cent), vascular loop (30, five per cent), basilar artery ectasia (13, two per cent), multiple high signal areas (135, 21 per cent), brain atrophy (52, eight per cent), sinus findings (56, nine per cent), middle ear/mastoid disease (34, five per cent), and a variety of other findings (39, six per cent) including clinically serious lesions (11, two per cent). The significance and management of these incidental findings is discussed. The majority were not clinically significant but the occasional presence of a serious incidental pathology should be borne in mind. Basilar artery ectasia and multiple high signal areas may be responsible for the symptoms investigated by MRI, and screening for cerebrovascular disease risk factors in such patients may be appropriate.

Middle-ear tumours are not uncommonly mistaken for mastoiditis on presentation. We report a case of cerebellopontine angle non-Hodgkin’s B-cell lymphoma originally presenting as a middle-ear inflammatory process. In mastoiditis not resolving with conventional treatment it is important to look for an underlying cause.

We report the contrast-enhanced magnetic resonance imaging (MRIg) findings from a series of 1139 patients who underwent screening to exclude a diagnosis of vestibular schwannoma. An acoustico-facial nerve bundle tumour was found in 3.1 per cent of patients imaged and vestibular schwannoma incidence is estimated at 1.4 per 100 000 population per annum. MRIg showed an abnormality in 14 per cent of patients; about one third of the findings may have accounted for the presenting symptom(s). A small number of patients had unexpected pathology revealed that required onward referral for further active management.

Primary malignant lymphoma is an uncommon disease of the central nervous system (CNS). Immunocompromised patients are at high risk of development of malignant lymphoma. We describe a case of primary CNS lymphoma presenting as a solitary cerebellopontine angle lesion. The patient had undergone extirpation of rectal cancer four years previously. Malignant lymphoma presenting as a cerebellopontine angle mass is extremely rare, with only 10 such cases (seven were primary, and the others secondary) previously reported.

We report a case of a 40-year-old man presenting with acute vertigo and deafness. Computed tomography (CT) scanning at initial presentation was normal. However, one year later he developed numbness on the right side of his face and examination revealed fifth, seventh and eighth cranial nerve palsies as well as cerebellar dysfunction. Magnetic resonance imaging (MRI) demonstrated a cerebellopontine angle lesion. He underwent near total excision followed by neuro-axis irradiation. The main mass of the tumour projected into the cerebellopontine angle. Histology showed this to be a medulloblastoma. All features of this case are unusual; hence we discuss the pathogenesis and management of this very rare tumour.

The aim of this study was the determination of the incidence of symptoms of audio-vestibular dysfunction and of abnormalities on audio-vestibular testing in patients found to have a unilateral meningioma of the cerebello-pontine angle (CPA). The case notes of 25 patients diagnosed with unilateral, sporadic and histologically proven CPA meningioma were retrospectively reviewed. The age range of this series was 31–71 years, with a mean age of 50 years. Two patients were male (eight per cent) and 23 were female (92 per cent). The mean length of history was 44.7 months. The distribution of tumour size was skewed toward larger tumours, with 15 cases (60 per cent) having tumours with a maximum diameter greater than 3.5 cm on imaging. Pure tone audiometry was normal in five cases (20 per cent), and no patients exhibited the high frequency sensorineural hearing loss that is characteristic of vestibular schwannoma. Speech audiometry was normal in 50 per cent of cases. Caloric testing was abnormal in 77 per cent of the 18 cases tested, whilst auditory brainstem responses (ABR) were abnormal in 100 per cent of the 18 cases who had sufficient hearing for this test to be possible. The presence of normal audiometry in patients with a proven CPA lesion indicates that, if in a protocol for investigation, asymmetry of hearing is mandatory then some pathology will be missed. Any suspicion of a CPA lesion warrants investigation even in the absence of hearing loss.

The investigation of choice for the identification of CPA lesions has become magnetic resonance imaging (MRI). If this technique is not available then this study indicates that ABR is a suitable and sensitive investigation. It should be borne in mind however that the data in this study has been derived from a series of predominantly large tumours, and the sensitivity of ABR to smaller CPA meningiomata may fall, as is the case for vestibular schwannoma.

Metastatic lesions in the cerebellopontine angle are rare. We encountered one such metastatic lesion from clearcell renal carcinoma that had a striking clinical appearance, bleeding from the ear and multiple lower cranial nerves' involvement. While the overall prognosis in CNS metastasis from systemic malignancy is gloomy, useful palliation can be achieved in patients with solitary lesions.

A 54 year old woman presenting to the psychiatric services with persecutory delusions, complex visual hallucinations and fluctuating levels of consciousness was discovered to have a meningioma occupying the cerebellopontine angle. The psychiatric symptomatology of cerebellopontine angle lesions is reviewed and the pathogenic mechanisms are explored in the light of the symptomatology observed.

Epidermoids are the third most common cerebellopontine angle tumour, and their diagnosis in the last two decades has been largely obtained using computed tomography (CT). More recently magnetic resonance imaging (MRI) has become a valuable diagnostic tool, and the signal characteristics and enhancement pattern of an epidermoid following intravenous gadolinium with MRI is presented and the literature reviewed.