Other Cerebellopontine Angle Tumors — MCQs
The most common tumor of the cerebellopontine angle is -
In a patient with acoustic neuroma all are seen except:
Which of the following statements about meningiomas is true?
Identify the condition shown in the CT scan image.
Which imaging modality is most effective in differentiating between epidermoid cyst and arachnoid cyst?
A 45-year-old female complains of progressive lower limb weakness, spasticity, and urinary hesitancy. MRI shows an intradural enhancing mass lesion in the spinal cord. MOST likely diagnosis is:
A 68-year-old man has many months history of progressive hearing loss, unsteady gait, tinnitus, and facial pain. An MRI scan reveals a tumor at the cerebellopontine angle. Which of the following cranial nerves is this tumor most likely to affect?
A false positive fistula test is associated with which of the following conditions?
A 10-year-old boy presented with sensorineural deafness not benefited with a hearing aid. What is the next treatment?
A glomus tumor is invading the visceral part of the carotid canal. It is classified as which type?
Other Cerebellopontine Angle Tumors Indian Medical PG Practice Questions and MCQs
Question 1: The most common tumor of the cerebellopontine angle is -
- A. None of the options
- B. Meningioma
- C. Acoustic neuroma (Correct Answer)
- D. Neurofibroma
Explanation: ***Acoustic neuroma*** - Acoustic neuromas, also known as **vestibular schwannomas**, are the most common tumors of the **cerebellopontine angle (CPA)**, accounting for **80-90%** of CPA tumors. [1] - They arise from the **Schwann cells** of the **vestibular portion of cranial nerve VIII** (vestibulocochlear nerve). [1] - Typical clinical presentation includes **progressive unilateral sensorineural hearing loss**, **tinnitus**, **vertigo**, and in advanced cases, involvement of adjacent cranial nerves (V and VII). *Meningioma* - Meningiomas are the **second most common** CPA tumor (10-15% of cases), originating from the **arachnoid cap cells**. [1] - They typically grow more slowly than acoustic neuromas and may present with different cranial nerve deficits depending on their exact location. - On imaging, they show characteristic **dural tail sign** and homogeneous enhancement. *Neurofibroma* - While neurofibromas can affect cranial nerves, they are **far less common** in the CPA than acoustic neuromas. [1] - They are often associated with **Neurofibromatosis type 1 (NF1)**, whereas bilateral acoustic neuromas are characteristic of **NF2**. [1] - Isolated CPA neurofibromas are rare. *None of the options* - This option is incorrect as **acoustic neuroma** is the well-established most common tumor of the cerebellopontine angle. [1] - This is a fundamental concept in neurology, neurosurgery, and pathology. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 727-728.
Question 2: In a patient with acoustic neuroma all are seen except:
- A. Cerebellar signs
- B. Facial nerve may be involved with unilateral deafness
- C. Reduced corneal reflex
- D. Acute episode of vertigo (Correct Answer)
Explanation: Acoustic neuroma typically presents with unilateral progressive hearing loss and sometimes tinnitus [1]. While acoustic neuromas can cause unsteadiness and gait imbalance due to gradual growth, they typically do not present with acute, severe, isolated vertigo because slow growth allows compensatory brainstem mechanisms to develop [1]. Acute vertigo is more characteristic of peripheral vestibular disorders like benign paroxysmal positional vertigo (BPPV) or Meniere's disease. As an acoustic neuroma (vestibular schwannoma) grows, it can compress the adjacent cerebellum, leading to cerebellar signs [1]. These signs include ataxia, dysmetria, and nystagmus, reflecting cerebellar dysfunction. The facial nerve (CN VII) runs in close proximity to the vestibulocochlear nerve (CN VIII), so it can be affected by an acoustic neuroma, leading to facial paresis or paralysis, though facial weakness is unusual at presentation [1]. Unilateral deafness is a classic and early symptom of acoustic neuroma due to compression of the cochlear portion of CN VIII [1]. The trigeminal nerve (CN V) has sensory innervation to the cornea, and its fibers pass near the cerebellopontine angle where acoustic neuromas grow. Compression of the trigeminal nerve by the tumor can lead to a reduced or absent corneal reflex on the affected side.
Question 3: Which of the following statements about meningiomas is true?
- A. Approximately 5% of meningiomas are malignant.
- B. Arise from the dural layer
- C. Meningiomas are more common in women due to hormonal influences.
- D. 95% cure rate following total surgical resection of benign meningiomas (Correct Answer)
Explanation: ***95% cure rate following treatment*** - Meningiomas generally have a **high cure rate of approximately 95%** following surgical resection, especially when they are completely excised [1]. - They are typically **benign tumors**, resulting in favorable outcomes with appropriate management [1]. *Arise from arachnoid layer* - Meningiomas actually arise from **meningothelial cells** of the **arachnoid layer**, but this statement does not fully explain their pathogenesis. - This mischaracterization does not provide an accurate understanding of the tumor's origin and biology. *50% are malignant* - Most meningiomas are benign; only a small percentage, about **1-5%**, are classified as malignant. - Thus, stating that **50% are malignant** significantly overestimates the incidence of aggressive forms. *More common in men* - Meningiomas are more prevalent in **women**, especially those aged between 30-70 years, with a female-to-male ratio of approximately **3:1**. - This option is incorrect as it misrepresents the demographic distribution of the disease. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1316-1317.
Question 4: Identify the condition shown in the CT scan image.
- A. None of the options
- B. Dandy-Walker malformation (Correct Answer)
- C. Cerebellar vermis hypoplasia
- D. Mega cisterna magna
Explanation: ***Dandy-Walker malformation*** - The image shows an enlarged posterior fossa with **cystic dilation of the fourth ventricle** and **absence/hypoplasia of the cerebellar vermis**, which are classic features of Dandy-Walker malformation. - The elevated tentorium and upward displacement of the transverse sinuses are also characteristic, contributing to the distinct appearance. *Cerebellar vermis hypoplasia* - While cerebellar vermis hypoplasia is a component of Dandy-Walker malformation, it is not the sole, defining feature. - Dandy-Walker also includes cystic dilation of the fourth ventricle and an enlarged posterior fossa, which are evident in the image and go beyond isolated vermis hypoplasia. *Mega cisterna magna* - A **mega cisterna magna** is a benign enlargement of the cisterna magna, which is the space between the cerebellum and the medulla oblongata. - Unlike in Dandy-Walker malformation, a mega cisterna magna usually does not involve displacement of the tentorium or hypoplasia of the cerebellar vermis, and the fourth ventricle is typically normal in shape and size. *None of the options* - The image clearly displays the diagnostic hallmarks of Dandy-Walker malformation, making this option incorrect.
Question 5: Which imaging modality is most effective in differentiating between epidermoid cyst and arachnoid cyst?
- A. Magnetic Resonance Imaging (MRI) (Correct Answer)
- B. Ultrasound (USG)
- C. Computed Tomography (CT) scan
- D. Positron Emission Tomography (PET) scan
Explanation: ***Magnetic Resonance Imaging (MRI)*** - **MRI** is superior for differentiating epidermoid and arachnoid cysts due to its excellent **soft tissue contrast** and ability to detect fluid signal characteristics. - **Diffusion-weighted imaging (DWI)**, a specific MRI sequence, is crucial; **epidermoid cysts** show high signal on DWI (diffusion restriction) due to their keratin content, while **arachnoid cysts** follow CSF signal on all sequences and do not restrict diffusion. *Ultrasound (USG)* - **Ultrasound** has limited utility for intracranial lesions in adults due to the bony skull, which prevents sound wave penetration. - It may be used in infants through the fontanelles but lacks the resolution and specific sequences needed to characterize these cysts. *Computed Tomography (CT) scan* - While a **CT scan** can identify these cysts as hypodense lesions, it lacks the detailed **tissue characterization** and signal patterns provided by MRI. - Both cysts would appear as **hypodense lesions**, making differentiation difficult based on density alone, especially after contrast administration. *Positron Emission Tomography (PET) scan* - A **PET scan** primarily assesses metabolic activity and would not effectively differentiate between benign **non-metabolic cysts** like epidermoid and arachnoid cysts. - It is more commonly used for detecting **malignancies** or assessing brain activity patterns, not for structural differentiation of fluid-filled lesions.
Question 6: A 45-year-old female complains of progressive lower limb weakness, spasticity, and urinary hesitancy. MRI shows an intradural enhancing mass lesion in the spinal cord. MOST likely diagnosis is:
- A. Intradural lipoma
- B. Neuroepithelial cyst
- C. Meningioma (Correct Answer)
- D. Dermoid cyst
Explanation: ***Meningioma*** - Intradural enhancing mass lesion in the **spinal cord** with progressive neurological symptoms like **lower limb weakness**, **spasticity**, and **urinary hesitancy** are highly suggestive of a **spinal meningioma**, which is the most common intradural extramedullary tumor in middle-aged females. - Meningiomas are typically **dural-based tumors** that enhance homogeneously with contrast on MRI and cause spinal cord compression. *Intradural lipoma* - Intradural lipomas are typically **non-enhancing** lesions on MRI, composed of fat with high T1 signal intensity. - They are often congenital and may not present with such acute, progressive neurological deficits. - They do not show contrast enhancement. *Neuroepithelial cyst* - Neuroepithelial cysts, such as **arachnoid cysts**, are typically **non-enhancing** and follow cerebrospinal fluid (CSF) signal intensity on MRI. - They rarely present as an enhancing mass and are more likely to be asymptomatic or cause symptoms due to mass effect without enhancement. *Dermoid cyst* - Dermoid cysts are typically **non-enhancing** lesions that contain **fatty components** and other ectodermal derivatives. - While they can cause neurological symptoms due to mass effect, they do not present as an enhancing lesion on MRI. - They show restricted diffusion and may have a chemical meningitis if ruptured.
Question 7: A 68-year-old man has many months history of progressive hearing loss, unsteady gait, tinnitus, and facial pain. An MRI scan reveals a tumor at the cerebellopontine angle. Which of the following cranial nerves is this tumor most likely to affect?
- A. sixth cranial nerve
- B. eighth cranial nerve (Correct Answer)
- C. tenth cranial nerve
- D. fourth cranial nerve
Explanation: ***eighth cranial nerve*** - The **eighth cranial nerve (vestibulocochlear nerve)** is located in the **cerebellopontine angle** and is responsible for **hearing and balance**. [1], [2] - Symptoms like **progressive hearing loss, tinnitus, and unsteady gait (vertigo)** are classic signs of compression or damage to this nerve, often caused by an **acoustic neuroma (vestibular schwannoma)** in this region. [2], [3] - **CN VIII is the FIRST and MOST COMMONLY affected nerve** in cerebellopontine angle tumors, making it the correct answer. - The **facial pain** mentioned suggests compression of the **trigeminal nerve (CN V)** by a large tumor, which can occur as the tumor expands, but CN VIII remains the primary nerve affected. *sixth cranial nerve* - The **sixth cranial nerve (abducens nerve)** innervates the **lateral rectus muscle**, responsible for **abduction of the eye**. - Damage would typically result in **diplopia** and an inability to move the eye laterally, which is not described. - This nerve is **rarely affected** by CPA tumors due to its anatomical location. *tenth cranial nerve* - The **tenth cranial nerve (vagus nerve)** controls **pharyngeal and laryngeal muscles**, as well as **parasympathetic innervation to many organs**. - Damage would typically cause **dysphagia**, **hoarseness**, or autonomic dysfunction, none of which are presented. - The vagus nerve is **not typically affected** by CPA tumors. *fourth cranial nerve* - The **fourth cranial nerve (trochlear nerve)** innervates the **superior oblique muscle**, aiding in **eye movement**. - Damage would primarily lead to **vertical diplopia**, particularly when looking down and in, which is not mentioned as a symptom. - This nerve is **not affected** by CPA tumors due to its location.
Question 8: A false positive fistula test is associated with which of the following conditions?
- A. Perilymph fistula
- B. Malignant sclerosis
- C. Congenital syphilis (Correct Answer)
- D. Cholesteatoma
Explanation: **Explanation:** The **Fistula Test** is used to identify an abnormal communication (fistula) between the inner and middle ear. A positive result occurs when pressure changes in the external auditory canal (via a Siegle’s speculum) induce nystagmus and vertigo. **1. Why Congenital Syphilis is correct:** In **Congenital Syphilis**, a "False Positive" fistula test occurs, also known as **Hennebert’s Sign**. It is considered "false" because there is no actual bony fistula present. Instead, the nystagmus is caused by: * **Fibrous adhesions** between the stapes footplate and the membranous labyrinth. * An abnormally **hypermobile stapes** footplate. Pressure is transmitted directly to the saccule, triggering the vestibular response despite an intact bony labyrinth. **2. Analysis of Incorrect Options:** * **Perilymph Fistula:** This is a **True Positive**. There is an actual breach in the oval or round window membrane, allowing pressure to affect the perilymph. * **Cholesteatoma:** This is the most common cause of a **True Positive** fistula test, typically due to erosion of the **Horizontal Semicircular Canal**. * **Malignant Sclerosis:** This is not a standard clinical term related to fistula testing. (Otosclerosis, however, usually results in a negative test unless complicated by other factors). **3. NEET-PG High-Yield Pearls:** * **Hennebert’s Sign:** Specifically refers to the false-positive fistula test in Congenital Syphilis or Meniere’s disease (due to fibrosis). * **Tullio Phenomenon:** Vertigo/nystagmus induced by **loud sounds**. Seen in Congenital Syphilis, Meniere’s, and Superior Semicircular Canal Dehiscence (SSCD). * **False Negative Test:** Occurs if the fistula is plugged by cholesteatoma/granulations or if the labyrinth is "dead" (non-functional).
Question 9: A 10-year-old boy presented with sensorineural deafness not benefited with a hearing aid. What is the next treatment?
- A. Cochlear implant (Correct Answer)
- B. Fenestromy
- C. Stapedectomy
- D. Stapes fixation
Explanation: **Explanation:** The patient is a 10-year-old child with **Sensorineural Hearing Loss (SNHL)** who has failed to benefit from conventional hearing aids. In cases of severe-to-profound SNHL where the auditory nerve is intact but the hair cells in the cochlea are non-functional, a **Cochlear Implant** is the gold standard treatment. It bypasses the damaged hair cells and directly stimulates the auditory nerve fibers electrically. **Analysis of Options:** * **A. Cochlear Implant (Correct):** Indicated for bilateral severe-to-profound SNHL when hearing aids provide inadequate benefit. In children, early implantation is crucial for speech and language development. * **B. Fenestromy:** This is an obsolete surgical procedure formerly used for otosclerosis (conductive hearing loss) to create a new window in the labyrinth. It has no role in treating SNHL. * **C. Stapedectomy:** This is the treatment of choice for **Otosclerosis**, which presents as **Conductive Hearing Loss (CHL)** due to stapes fixation. It involves replacing the stapes with a prosthesis and is contraindicated in SNHL. * **D. Stapes Fixation:** This is a pathological condition (clinical finding in otosclerosis), not a treatment modality. **High-Yield Clinical Pearls for NEET-PG:** * **Ideal Age for Implantation:** The earlier, the better (usually >12 months) to utilize the brain's neuroplasticity for language acquisition. * **Prerequisite:** A patent cochlea and a functional **Cochlear Nerve (CN VIII)** must be present (confirmed via MRI). * **Auditory Brainstem Implant (ABI):** Indicated if the cochlear nerve is absent or destroyed (e.g., Bilateral Acoustic Neuroma/NF2). * **Hennebert’s Sign:** False positive fistula test seen in Meniere’s or Congenital Syphilis; do not confuse with surgical indications.
Question 10: A glomus tumor is invading the visceral part of the carotid canal. It is classified as which type?
- A. Type B
- B. Type C1
- C. Type C2 (Correct Answer)
- D. Type C3
Explanation: This question tests your knowledge of the **Fisch Classification** for Glomus tumors (Paragangliomas), which is the gold standard for determining surgical approach based on anatomical extension. ### **Explanation of the Correct Answer** The Fisch classification categorizes tumors based on their involvement of the temporal bone and skull base. **Type C** tumors specifically involve the **infralabyrinthine compartment** and extend along the **carotid canal**. * **Type C1:** Destroys the bone of the carotid foramen but does not involve the carotid artery itself. * **Type C2:** Invades the **vertical (visceral) portion** of the carotid canal. * **Type C3:** Extends along the **horizontal portion** of the carotid canal. Since the question specifies invasion of the visceral (vertical) part of the carotid canal, **Type C2** is the correct classification. ### **Analysis of Incorrect Options** * **Type B:** These tumors are limited to the tympanomastoid area without involvement of the infralabyrinthine compartment or the carotid canal. * **Type C1:** This involves only the entrance (foramen) of the carotid canal, not the canal's vertical segment. * **Type D:** These tumors have **intracranial extension**. D1 involves extension <2cm, while D2 involves extension >2cm. ### **Clinical Pearls for NEET-PG** * **Glomus Jugulare:** Arises from the dome of the jugular bulb (Fisch Type C/D). * **Glomus Tympanicum:** Arises from the promontory (Fisch Type A). * **Phelp’s Sign:** Loss of the bony plate between the carotid canal and the jugular foramen on CT (indicative of Glomus Jugulare). * **Brown’s Sign:** Pulsatile blanching of the tympanic membrane on positive pressure with a Siegel’s speculum (Pathognomonic). * **Aquino’s Sign:** Blanching of the mass on carotid artery compression.
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