Skull Base Surgery Practice Questions

Q: A patient, who underwent lateral skull base surgery a few months prior, presents with complaints of recurrent aspirations. There is no change in voice. Which of the following nerves is most likely injured during the surgery?

Superior Laryngeal Nerve (SLN). **Explanation:** The key to this question lies in the dissociation between sensory loss and motor function of the vocal cords. **1. Why Superior Laryngeal Nerve (SLN) is correct:** The SLN divides into the Internal and External branches. The **Internal Laryngeal Nerve** provides sensory innervation to the laryngeal mucosa above the vocal folds. Injury to this nerve leads to **laryngeal anesthesia**, causing a loss of the cough reflex when food or liquid enters the laryngeal inlet. This results in **recurrent silent aspirations**. Since the External branch only supplies the cricothyroid muscle (which tenses the vocal cords), its injury may cause a slight change in pitch but **no hoarseness or loss of voice**, matching the clinical presentation. **2. Why other options are incorrect:** * **Vagus Nerve (Main Trunk):** Injury would involve both the SLN and RLN, leading to both aspiration and significant voice changes (vocal cord paralysis). * **Glossopharyngeal Nerve (CN IX):** While it mediates the gag reflex and oropharyngeal sensation, isolated injury is less likely to cause recurrent aspiration without dysphagia or loss of taste in the posterior third of the tongue. * **Recurrent Laryngeal Nerve (RLN):** This nerve provides motor supply to all intrinsic muscles of the larynx (except the cricothyroid). Injury would cause **vocal cord palsy**, leading to a breathy voice or hoarseness, which is absent in this patient. **Clinical Pearls for NEET-PG:** * **Internal Laryngeal Nerve:** "The Watchdog of the Larynx"—its loss leads to aspiration. * **Cricothyroid Muscle:** The only intrinsic laryngeal muscle supplied by the External Laryngeal Nerve; it is the "tuning fork" (increases pitch). * **Lateral Skull Base Surgery:** High risk for "Lower Cranial Nerve" (IX, X, XI, XII) palsies. Always check for the "Curtain Sign" (deviation of the posterior pharyngeal wall) to assess CN IX and X.

Q: A laparoscopic intranasal approach is used for accessing all of the following EXCEPT?

Cerebellum. **Explanation:** The **Endoscopic Endonasal Approach (EEA)** is a minimally invasive surgical technique that utilizes the natural corridor of the nasal cavity and sinuses to access the skull base. **Why Cerebellum is the Correct Answer:** The cerebellum is located in the **posterior cranial fossa**, situated behind the brainstem and beneath the tentorium cerebelli. While endoscopic endonasal approaches can reach the clivus (anterior to the brainstem), they cannot safely bypass the brainstem and major vascular structures to access the cerebellum. The cerebellum is traditionally accessed via a **suboccipital craniotomy** or retrosigmoid approach. **Analysis of Incorrect Options:** * **Lacrimal Sac (A):** Accessed via **Endoscopic Dacryocystorhinostomy (DCR)**. The sac lies lateral to the lateral nasal wall (near the agger nasi cell), making it easily accessible intranasally. * **Pituitary Gland (C):** This is the classic indication for the **Transsphenoidal approach**. The sella turcica forms the posterior-superior limit of the sphenoid sinus. * **Optic Nerve (D):** The optic nerve can be accessed for **decompression** (e.g., in traumatic optic neuropathy or Graves' ophthalmopathy) via the medial wall of the orbit and the lateral wall of the sphenoid sinus (recess of the optic nerve). **High-Yield Clinical Pearls for NEET-PG:** * **Limits of EEA:** It can access the Anterior Fossa (Crista galli to Planum sphenoidale), Middle Fossa (Sella, Cavernous sinus), and the Upper Clivus. * **Critical Landmark:** The **Sphenoid Sinus** is the "gateway" to the skull base in endoscopic surgery. * **Optico-Carotid Recess (OCR):** A key landmark in the lateral wall of the sphenoid sinus; it is the space between the internal carotid artery and the optic nerve. * **CSF Leak:** The most common complication of expanded endonasal approaches; often repaired using a **Hadad-Bassagasteguy flap** (nasoseptal flap based on the posterior septal artery).

Q: All of the following statements about Sternberg canal are true, except?

Located posterior and lateral to the Foramen Rotundum. ### Explanation **Sternberg’s Canal** (also known as the lateral craniopharyngeal canal) is a rare congenital bony defect in the lateral wall of the sphenoid sinus. It results from the incomplete fusion of the **greater wing of the sphenoid** (alisphenoid) with the **basisphenoid**. #### Why Option B is the Correct Answer (The False Statement) The Sternberg canal is anatomically located **medial and anterior** to the **Foramen Rotundum**. Therefore, the statement claiming it is "posterior and lateral" is anatomically incorrect. Understanding this relationship is crucial for skull base surgeons to avoid neurovascular injury during endoscopic repairs. #### Analysis of Other Options * **Option A:** This is a **true** statement regarding its anatomical position relative to the Foramen Rotundum. * **Option C:** It is a **true** developmental concept. It represents a persistent lateral craniopharyngeal canal due to a failure of ossification between the components of the sphenoid bone. * **Option D:** This is a **true** clinical manifestation. The canal provides a pathway for the herniation of meninges and brain tissue into the sphenoid sinus, leading to **intrasphenoidal encephaloceles** or spontaneous **CSF rhinorrhea**. #### High-Yield Clinical Pearls for NEET-PG * **Triad of Sternberg Canal:** Spontaneous CSF rhinorrhea, intrasphenoidal meningocele, and a bony defect lateral to the sphenoid sinus. * **Radiology:** On a CT scan, look for a defect in the lateral recess of the sphenoid sinus, medial to the Foramen Rotundum. * **Surgical Significance:** It is a common site for "spontaneous" CSF leaks. Unlike traumatic leaks, these often require an endoscopic endonasal approach for multilayered repair. * **Differential:** Do not confuse it with the **Canal of Civinini** (pterygospinous malformation) or the **Vidian canal** (which is inferior to the Foramen Rotundum).

Q: A female in the emergency department is found to have CSF rhinorrhea following a motor vehicle accident. What is the first-line treatment for CSF rhinorrhea in this patient?

Observation for 7-10 days with antibiotic therapy. **Explanation:** The management of traumatic CSF rhinorrhea follows a conservative-first approach. Most post-traumatic CSF leaks (approximately 85-90%) resolve spontaneously within 7 to 10 days with conservative management. **Why Option D is Correct:** The first-line treatment for acute traumatic CSF rhinorrhea is **conservative management**. This involves bed rest with the head end elevated (30-45 degrees) to decrease intracranial pressure, avoidance of straining (using stool softeners), and avoiding nose blowing. While the use of prophylactic antibiotics is debated in some literature, in the context of standard NEET-PG patterns, observation for 7-10 days remains the primary initial step to allow the dural tear to heal spontaneously. **Why Other Options are Incorrect:** * **Option A:** Plugging the nose is strictly contraindicated as it can lead to the accumulation of CSF, increasing the risk of retrograde infection and **meningitis** or causing a tension pneumocephalus. * **Option B:** Forceful blowing increases intracranial pressure and can force air into the cranial cavity (pneumocephalus) or push bacteria from the nasal cavity into the meninges. * **Option C:** Surgery (Craniotomy or Endoscopic repair) is reserved for cases where conservative management fails after 1-2 weeks, or in cases of high-flow leaks and intracranial complications. **High-Yield Clinical Pearls for NEET-PG:** * **Most common site of traumatic CSF leak:** Cribriform plate/Ethmoid roof. * **Confirmatory Test:** Detection of **Beta-2 Transferrin** (most specific) or Beta-trace protein in the fluid. * **Target Sign/Halo Sign:** On a paper/linen, CSF forms a clear outer ring around a central spot of blood. * **Investigation of Choice (Localization):** High-Resolution CT (HRCT) of the temporal bone/paranasal sinuses. * **Reservoir Sign:** A gush of fluid when the patient leans forward (Tea-pot sign).

Q: An 18-year-old boy has presented with a tumour originating from the clivus. Diagnosis is: (DNB Pattern 2018)

Chordoma. ***Chordoma*** - **Chordomas** are rare, slow-growing malignant bone tumors thought to arise from remnants of the **notochord**, which contributes to the formation of the vertebral column and the base of the skull. - These tumors most commonly occur at the **clivus** (base of the skull) and the **sacrococcygeal region**, making a clival mass highly suspicious for chordoma in an 18-year-old. *Chloroma* - A **chloroma**, also known as a granulocytic sarcoma, is an extramedullary manifestation of **acute myeloid leukemia** (AML), presenting as a localized tumor of immature myeloid cells. - While it can occur anywhere, it is not typically associated with the clivus as a primary site, and there is no mention of a hematological malignancy. *Juvenile nasopharyngeal angiofibroma* - **Juvenile nasopharyngeal angiofibroma** (JNA) is a benign, highly vascular tumor that typically originates in the **nasopharynx** of adolescent males. - Although common in adolescent males and located in the head and neck, it arises from the nasopharynx, not primarily the clivus. *Meningioma* - A **meningioma** is a tumor that arises from the **meninges**, the membranes surrounding the brain and spinal cord. They are usually benign and more common in older adults. - While meningiomas can occur at the skull base and clivus, they are less common in young adults and usually present in older age groups compared to chordomas with clival involvement.

Question 1

A patient, who underwent lateral skull base surgery a few months prior, presents with complaints of recurrent aspirations. There is no change in voice. Which of the following nerves is most likely injured during the surgery?

Accepted Answer

Superior Laryngeal Nerve (SLN)

Answer

Vagus nerve

Answer

Glossopharyngeal nerve

Answer

Recurrent Laryngeal Nerve (RLN)

Question 2

A laparoscopic intranasal approach is used for accessing all of the following EXCEPT?

Accepted Answer

Cerebellum

Answer

Lacrimal sac

Answer

Pituitary gland

Answer

Optic nerve

Question 3

All of the following statements about Sternberg canal are true, except?

Accepted Answer

Located posterior and lateral to the Foramen Rotundum

Answer

Located anterior and medial to the Foramen Rotundum

Answer

Represents a persistent craniopharyngeal canal

Answer

Causes an intrasphenoidal meningocele

Question 4

A female in the emergency department is found to have CSF rhinorrhea following a motor vehicle accident. What is the first-line treatment for CSF rhinorrhea in this patient?

Accepted Answer

Observation for 7-10 days with antibiotic therapy

Answer

Immediate plugging of the nose with petroleum gauze

Answer

Forceful blowing of the nose

Answer

Craniotomy

Question 5

An 18-year-old boy has presented with a tumour originating from the clivus. Diagnosis is: (DNB Pattern 2018)

Accepted Answer

Chordoma

Answer

Chloroma

Answer

Juvenile nasopharyngeal angiofibroma

Answer

Meningioma

Skull Base Surgery — MCQs

Skull Base Surgery — MCQs

On this page

Practice by Chapter

Want unlimited practice?