Cerebellopontine angle syndrome

Overview

Cerebellopontine angle (CPA) syndrome refers to a collection of neurological symptoms that result from lesions located in the cerebellopontine angle, a region of the brain at the junction of the cerebellum and pons. This area contains critical structures, including cranial nerves (especially cranial nerves VII and VIII), blood vessels, and cerebrospinal fluid pathways. Lesions in this space, most commonly benign tumors, can compress these structures, leading to auditory, vestibular, and facial nerve dysfunction.

Causes

The most frequent cause of cerebellopontine angle syndrome is a benign tumor, but other masses or abnormalities can also affect this region. Common causes include:

• Vestibular schwannoma (acoustic neuroma): The most common CPA tumor, arising from the vestibular branch of cranial nerve VIII

• Meningioma: A tumor originating from the meninges lining the brain

• Epidermoid cyst: A congenital lesion that grows slowly and may compress cranial nerves

• Arachnoid cyst: A fluid-filled cavity within the arachnoid membrane

• Brainstem gliomas or metastases: Rare, but possible causes

• Vascular malformations: Such as aneurysms or arteriovenous malformations in the CPA region

Symptoms

Symptoms of CPA syndrome depend on the size and location of the lesion and which structures are compressed. Common clinical features include:

• Hearing loss: Usually unilateral and progressive, due to involvement of the cochlear nerve (CN VIII)

• Tinnitus: Ringing or buzzing sound in the affected ear

• Vertigo or imbalance: Resulting from vestibular nerve (CN VIII) dysfunction

• Facial numbness or pain: From compression of the trigeminal nerve (CN V)

• Facial weakness or twitching: Due to involvement of the facial nerve (CN VII)

• Headache: May occur due to increased intracranial pressure

• Double vision, hoarseness, or dysphagia: In large lesions affecting lower cranial nerves (CNs IX–XII)

• Ataxia or coordination issues: From cerebellar compression

Diagnosis

Diagnosis of cerebellopontine angle syndrome involves a combination of neurological assessment and imaging studies:

• Neurological examination: To assess cranial nerve function, hearing, balance, and facial sensation

• Audiometry: Hearing tests to identify sensorineural hearing loss

• Brain MRI with contrast: The gold standard imaging tool to visualize CPA lesions

• CT scan: May be used to evaluate bone involvement or when MRI is contraindicated

• Vestibular testing: Including videonystagmography (VNG) or electronystagmography (ENG)

Treatment

Treatment of CPA syndrome depends on the nature, size, and progression of the lesion, as well as the patient's symptoms and overall health. Options include:

• Observation: Small, asymptomatic tumors (especially vestibular schwannomas) may be monitored with serial MRIs

• Surgical removal: Indicated for larger or symptomatic tumors; approaches include retrosigmoid, translabyrinthine, or middle fossa craniotomy

• Radiation therapy: Stereotactic radiosurgery (e.g., Gamma Knife) may be used for small to medium-sized tumors or in patients unfit for surgery

• Medical management: For symptom control, such as anti-vertigo medications or corticosteroids to reduce swelling

• Rehabilitation: Physical therapy, vestibular rehab, and hearing aids or cochlear implants in select cases

Prognosis

The prognosis for cerebellopontine angle syndrome depends on the underlying cause and the timing of treatment. Most vestibular schwannomas are benign and slow-growing, and when treated early, outcomes are generally favorable. However, large tumors or delayed diagnosis may result in permanent cranial nerve deficits, hearing loss, or brainstem compression. Modern surgical and radiologic techniques have significantly improved functional preservation, especially of hearing and facial nerve function. Regular follow-up is essential to monitor for recurrence or progression.