From the Guidelines
Schwannomas most commonly occur in the cerebellopontine angle (CPA) compartment, which is located at the junction of the cerebellum and pons in the posterior cranial fossa. This is based on the most recent evidence from the study published in Neuro-Oncology in 2020 1. Specifically, vestibular schwannomas (acoustic neuromas) arise from the vestibular portion of the eighth cranial nerve (vestibulocochlear nerve) as it traverses the internal auditory canal before entering the CPA.
Some key points to consider about schwannomas in the CPA compartment include:
- They account for approximately 80% of tumors in the cerebellopontine angle 1
- They can cause unilateral sensorineural hearing loss, tinnitus, and vestibular symptoms such as vertigo and unsteadiness 1
- Large tumors may cause trigeminal and facial neuropathies as well as brainstem compression and hydrocephalus 1
- The development of schwannomas is related to mutations in the NF2 gene, which encodes for the protein merlin that normally functions as a tumor suppressor 1
It's also worth noting that while the CPA is the most common location for schwannomas, they can also develop in other compartments, including peripheral nerves throughout the body, spinal nerve roots, and less commonly other cranial nerves such as the trigeminal nerve (CN V) 1. However, the cerebellopontine angle remains the most common and well-established location for these tumors.
From the Research
Schwannoma Compartment
- The compartment of a schwannoma can vary depending on its location and type.
- Vestibular schwannomas, for example, are typically found in the cerebellopontine angle (CP angle) 2.
- Trigeminal schwannomas, on the other hand, can arise from anywhere between the root and the distal extracranial branches of the trigeminal nerve 3.
- Jugular foramen schwannomas are found in the jugular foramen, which is located in the posterior fossa 4.
Posterior Fossa Morphometry
- The morphometry of the posterior fossa can affect the extent of excision of CP angle acoustic schwannomas 5.
- Studies have shown that the inter-sigmoid distance and the petrous-apex angle are greater in Indian populations compared to European populations 5.
- These differences in posterior fossa morphometry can impact the surgical approach and outcome for patients with schwannomas in this region.
Clinical Implications
- Accurate diagnosis and localization of schwannomas are crucial for determining the best course of treatment 2, 3, 4, 6.
- Stereotactic radiosurgery (SRS) is a minimally invasive alternative or adjunct to microsurgery for schwannomas, and has been shown to be effective in controlling tumor growth and preserving cranial nerve function 4, 6.