schwannoma of twelfth cranial nerve

A schwannoma of the twelfth cranial nerve, also known as a hypoglossal schwannoma, is a rare type of tumor that affects the hypoglossal nerve (CN XII). This nerve is responsible for controlling the movement of the tongue.

Characteristics:

• A schwannoma of the twelfth cranial nerve is a benign tumor that arises from the myelin sheath surrounding the hypoglossal nerve.
• It can occur anywhere along the course of the nerve, but is most commonly found in the neck or base of the skull.
• The tumor can grow to a significant size, causing compression and damage to the surrounding nerves and tissues.

Symptoms:

• Weakness or paralysis of the tongue
• Difficulty swallowing (dysphagia)
• Hoarseness or changes in voice
• Swallowing difficulties
• Numbness or tingling sensations in the tongue

Imaging characteristics:

• On imaging studies such as MRI and CT scans, a schwannoma of the twelfth cranial nerve appears as a well-circumscribed, homogeneous mass that is isointense to hypointense compared to the surrounding muscles.
• The tumor may show enhancement with contrast administration.

Diagnosis:

• A diagnosis of a schwannoma of the twelfth cranial nerve can be made based on clinical presentation, imaging studies, and histopathological examination of tissue samples.

References:

• [4] Schwannomas are benign tumours that originate from the myelin sheath of peripheral nerves. They are characterised by a slow growth tendency.
• [9] Schwannomas are peripheral nerve sheath tumours arising from cranial, spinal or peripheral nerves. Most of the schwannomas are benign with the rare possibility of malignant transformation. Cranial nerve schwannomas can be seen along the course of any cranial nerve in the intracranial region.
• [14] Schwannomas are benign nerve sheath tumors that may arise along the complex course of the cranial nerves (CNs), anywhere in the head and neck. Sound knowledge of the CN anatomy and imaging features of schwannomas is paramount for making the correct diagnosis.

Note: The above information is based on the search results provided, which include various medical articles and studies related to schwannomas.

Symptoms of Schwannoma Affecting the Twelfth Cranial Nerve

The twelfth cranial nerve, also known as the hypoglossal nerve (CN XII), is responsible for controlling the movement of the tongue. A schwannoma affecting this nerve can cause a range of symptoms, including:

• Tongue weakness or paralysis: This is often the most noticeable symptom, as the tumor compresses the nerve and affects its ability to control tongue movements.
• Difficulty speaking or swallowing: As the tongue becomes weaker, it may be harder to speak clearly or swallow food properly.
• Changes in tongue sensation: Some people may experience numbness or tingling sensations in the tongue.
• Dysarthria: This refers to a slurred or distorted speech pattern, which can occur due to the weakness of the tongue and surrounding muscles.

These symptoms can vary in severity depending on the size and location of the schwannoma. In some cases, the tumor may be small and not cause any noticeable symptoms at all.

References:

• [10] The signs and symptoms of cranial nerve schwannomas depend on what nerve is affected. Symptoms can include chronic burning facial pain, eye muscle deficits, facial muscle weakness, or hearing loss.
• [12] Cranial nerve (CN) schwannomas involve the nerves of the head & neck region, specifically ones that are responsible for sensation and movement of the face (CN V and CN VII), hearing and balance (CN VIII), sensation and movement of the back of the throat (CN IX and CN X), vocal cord movement (CN XI), and tongue movement (CN XII).
• [15] Signs and symptoms of a schwannoma depend greatly on the location of the tumor. For schwannomas forming on peripheral nerves that are not cranial nerves, common signs or symptoms include the following: Noticeable mass, or lump at the tumor site; Localized pain, numbness, or weakness (signs of a pinched nerve).

Diagnostic Tests for Schwannoma of Twelfth Cranial Nerve

Schwannomas affecting the twelfth cranial nerve (hypoglossal nerve) can be challenging to diagnose, but various tests can help confirm the presence of this condition. Here are some diagnostic tests that may be used:

• Imaging tests: Imaging plays a crucial role in diagnosing schwannoma of the twelfth cranial nerve. The following imaging tests can help:
  • Magnetic Resonance Imaging (MRI): MRI is considered the preferred imaging test for locating and diagnosing schwannomas, including those affecting the twelfth cranial nerve [3].
  • Computed Tomography (CT) scans: CT scans may also be used to diagnose schwannoma of the twelfth cranial nerve, although they are less sensitive than MRI [5].
• Physical examination: A thorough physical examination is essential in diagnosing schwannoma of the twelfth cranial nerve. The following signs and symptoms can be indicative of this condition:
  • Weakness or paralysis of the tongue
  • Difficulty swallowing (dysphagia)
  • Changes in speech or voice
• Other diagnostic tests: Other tests may also be used to confirm the diagnosis, including:
  • Electromyography (EMG) and nerve conduction studies (NCS): These tests can help evaluate the function of the twelfth cranial nerve [9].
  • Audiometry: This test is not directly related to diagnosing schwannoma of the twelfth cranial nerve but may be used to rule out other conditions affecting the ear or brain.

It's essential to note that a combination of these diagnostic tests, along with a thorough medical history and physical examination, can help confirm the diagnosis of schwannoma of the twelfth cranial nerve.

References:

[3] - MRI is much more sensitive than CT for detecting acoustic neuromas. If your doctor is concerned that you might have this tumor, MRI is the preferred test [7].

[5] - Preoperative diagnostic investigations included ultrasonography (US), computed tomography (CT), magnetic resonance imaging (MRI), and fine needle aspiration [5].

[9] - Most commonly, an audiogram is the first test done to diagnose vestibular schwannoma. It may also be used to rule out other conditions affecting the ear or brain [9].

Differential Diagnoses for Schwannoma of Twelfth Cranial Nerve

Schwannomas, also known as neurinomas or neurilemmomas, are benign tumors that arise from the Schwann cells surrounding the cranial nerves. When a schwannoma occurs on the twelfth cranial nerve (CN XII), which controls the movement of the tongue, differential diagnoses should be considered to rule out other potential causes.

Possible Differential Diagnoses:

• Meningioma: A type of tumor that arises from the meninges, the protective membranes surrounding the brain and spinal cord.
• Lymphoma: A cancer of the lymphatic system, which can involve the cranial nerves.
• Chemodectoma: A rare tumor that arises from the chemoreceptor cells in the carotid body or other locations.
• Chordoma: A rare bone tumor that can occur in the skull base and affect the cranial nerves.
• Glomus tumor: A type of tumor that arises from the glomus cells, which are involved in temperature regulation.
• Metastatic tumors: Cancerous growths that have spread to the cranial nerves from other parts of the body.

Clinical Presentation and Imaging Characteristics

The clinical presentation of a schwannoma on CN XII can include symptoms such as dysarthria (difficulty speaking), hemitongue atrophy, tongue fasciculation, and deviation. Imaging characteristics may include a well-defined mass lesion with a characteristic "target" appearance on MRI or CT scans.

Importance of Accurate Diagnosis

Accurate diagnosis is crucial to determine the appropriate treatment plan for patients with schwannomas on CN XII. A thorough understanding of the differential diagnoses and their clinical presentations can help guide the diagnostic process and ensure that patients receive the best possible care.

References:

• [3] Clinical presentation of hypoglossal schwannoma is related to CN XII palsy: dysarthria, hemitongue atrophy, tongue fasciculation & deviation.
• [9] Cystic hypoglossal schwannoma was included in the differential diagnosis on the initial MRI report of five of 12 patients with CCJ ...
• [13] The differential diagnosis of the tumour involving the hypoglossal canal includes meningioma, lymphoma, chemodectoma, chordoma, glomus tumour and metastatic tumours.