Schwannomas are non-cancerous tumors that originate from Schwann cells, which form the myelin sheath around peripheral nerves. While benign in nature, their location within the nervous system can result in significant neurological complications.
The most frequently encountered form is the vestibular schwannoma (also known as acoustic neuroma), which arises from the eighth cranial nerve. These tumors can also occur along the spinal nerve roots, cranial nerves, or other peripheral nerves. Schwannomas represent approximately 6-8% of intracranial tumors and 25–30% of spinal intradural extramedullary tumors. Most cases are sporadic, although genetic conditions like Neurofibromatosis Type 2 (NF2) and schwannomatosis may increase susceptibility.
Histological and Molecular Insights
Microscopic examination reveals that schwannomas contain two distinctive structural patterns:
Antoni A areas: Densely packed spindle cells often arranged in parallel bundles with characteristic Verocay bodies.
Antoni B areas: Loosely organized cells set within a myxoid (gel-like) stroma, giving a more relaxed tissue appearance.
At the molecular level, mutations in the NF2 gene are commonly implicated. Loss of Merlin protein disrupts normal growth regulation and contributes to tumor formation. Such genetic alterations are observed in both sporadic vestibular schwannomas and NF2-associated tumors.
Clinical Presentation and Symptoms
The symptoms of schwannoma vary widely depending on tumor location and size:
Vestibular Schwannoma (Brain Schwannoma / Acoustic Neuroma)
Progressive hearing loss on the affected side.
Ringing in the ear (tinnitus).
Balance difficulties and dizziness.
Larger tumors may compress the facial nerve, causing weakness or sensory changes.
Spinal Schwannoma
Localized neck or back pain.
Radicular pain radiating to the limbs.
Numbness, tingling, or motor weakness.
Severe cases may include gait instability and bladder or bowel dysfunction.
Peripheral Nerve Schwannoma
Detectable localized mass, sometimes tender to touch.
Compression-related numbness or weakness in the associated nerve distribution.
Recognizing these schwannoma symptoms early is critical for timely diagnosis and optimal management.
Diagnostic Workup
Neurological Examination: A comprehensive evaluation of motor, sensory, cranial nerve, and reflex functions is essential.
In schwannoma radiology: imaging and functional assessments are essential for accurate diagnosis:
Magnetic Resonance Imaging (MRI): The preferred modality for identifying schwannomas. Vestibular schwannomas appear as well-defined, contrast-enhancing lesions originating in the internal auditory canal, whereas spinal schwannomas are typically intradural and extramedullary, attached to nerve roots.
Audiometry: Evaluates hearing function in patients with vestibular schwannomas.
Schwannoma Treatment
Management of schwannoma in brain and spinal regions is tailored to tumor characteristics, symptoms, and patient health:
1. Microsurgical Resection
Preferred for symptomatic or growing tumors. Vestibular schwannoma surgery aims to remove the tumor completely while preserving hearing and facial nerve function.
2. Stereotactic Radiosurgery (Gamma Knife, CyberKnife)
Minimally invasive option for small tumors. Highly effective in halting tumor progression while potentially maintaining hearing.
3. Active Surveillance (“Wait and Scan”)
Appropriate for small, slow-growing, or asymptomatic tumors.