Head Practice Questions

Q: Which of the following muscles is NOT an elevator of the mandible?

Digastric. The muscles of mastication are responsible for the movements of the mandible at the temporomandibular joint (TMJ). These movements include elevation (closing the mouth), depression (opening the mouth), protrusion, retraction, and side-to-side movements. ### **Explanation of the Correct Answer** **D. Digastric:** This is the correct answer because the digastric muscle (specifically the anterior belly) acts as a **depressor** of the mandible. When the hyoid bone is fixed by the infrahyoid muscles, the contraction of the digastric pulls the symphysis menti downward, helping to open the mouth. It is not an elevator. ### **Analysis of Incorrect Options (Elevators)** The "elevators" of the mandible are the primary muscles of mastication that close the jaw: * **A. Temporalis:** A fan-shaped muscle that elevates the mandible. Its posterior fibers also act as the primary retractor of the jaw. * **B. Medial Pterygoid:** Often called the "internal masseter," it forms a sling with the masseter to powerfully elevate the mandible. * **C. Masseter:** The most powerful muscle of mastication; its primary action is elevation. ### **High-Yield Clinical Pearls for NEET-PG** * **Innervation Rule:** All four primary muscles of mastication (Masseter, Temporalis, Medial, and Lateral Pterygoids) are supplied by the **Mandibular nerve (V3)**. * **The "Opener":** The **Lateral Pterygoid** is the only primary muscle of mastication that helps depress (open) the mandible. Remember: "Lateral Lowers." * **Digastric Nerve Supply:** This is a common exam favorite. The **Anterior belly** is supplied by the Nerve to Mylohyoid (V3), while the **Posterior belly** is supplied by the Facial Nerve (VII). * **Gravity:** While muscles like the digastric and lateral pterygoid assist, gravity is the primary force for jaw depression in a standing position.

Q: An 8-year-old boy had an extensive mastoidectomy due to an infection that did not respond to antibiotics. Postoperatively, he developed Bell's palsy (facial paralysis). A feature of this paralysis was the accumulation of saliva in the oral vestibule, leading to dribbling from the corner of his mouth. Which of the following muscles was paralyzed, causing this specific symptom?

Buccinator. ### Explanation **Correct Option: C. Buccinator** The clinical presentation describes **Bell’s palsy** (lower motor neuron facial nerve palsy) following mastoid surgery. The facial nerve (CN VII) is at risk during mastoidectomy as it traverses the facial canal in the petrous temporal bone. The **buccinator** muscle, supplied by the buccal branch of the facial nerve, forms the muscular substance of the cheek. Its primary functional role during mastication is to flatten the cheek against the teeth and gums. This action prevents food and saliva from accumulating in the **oral vestibule** (the space between the teeth/gums and the cheeks/lips) and directs it back toward the occlusal surfaces of the teeth. Paralysis of the buccinator leads to a loss of cheek tone, causing saliva and food boluses to pool in the vestibule, resulting in the characteristic dribbling seen in this patient. **Analysis of Incorrect Options:** * **A. Zygomaticus major:** This muscle draws the angle of the mouth upward and backward (smiling). While paralyzed in Bell’s palsy, it does not control the accumulation of fluids in the vestibule. * **B. Orbicularis oculi:** This muscle is responsible for closing the eyelids. Paralysis leads to *lagophthalmos* (inability to close the eye), not oral symptoms. * **D. Levator palpebrae superioris:** This muscle elevates the upper eyelid and is supplied by the **Oculomotor nerve (CN III)**. It is not affected in facial nerve palsy. **High-Yield Clinical Pearls for NEET-PG:** * **Hyperacusis:** Occurs in facial nerve palsy if the nerve to the **stapedius** is involved (loss of dampening of sound). * **Chorda Tympani involvement:** Leads to loss of taste (ageusia) on the anterior 2/3rd of the tongue and reduced salivation (submandibular/sublingual glands). * **Mastoid Surgery Risk:** The facial nerve is most commonly injured in its **tympanic (horizontal)** or **mastoid (vertical)** segments during middle ear surgeries.

Q: A 55-year-old woman has undergone facial surgery for the excision of a malignant parotid tumor. A week postoperatively, marked weakness is seen in the musculature of the patient's lower lip. Which of the following nerves was most likely injured during the parotidectomy?

Marginal mandibular branch of facial. **Explanation:** The **facial nerve (CN VII)** provides motor innervation to the muscles of facial expression. After exiting the stylomastoid foramen, it enters the parotid gland and divides into five terminal branches: Temporal, Zygomatic, Buccal, Marginal Mandibular, and Cervical. 1. **Why Option A is correct:** The **Marginal Mandibular branch** supplies the muscles of the lower lip, specifically the *depressor anguli oris*, *depressor labii inferioris*, and *mentalis*. Injury to this nerve during parotid surgery is a known complication that results in drooping of the corner of the mouth and weakness in depressing the lower lip, leading to an asymmetrical smile. 2. **Why other options are incorrect:** * **Zygomatic branch:** Supplies the orbicularis oculi; injury would cause inability to close the eye tightly. * **Mandibular division of Trigeminal (V3):** Provides sensory innervation to the lower face and motor innervation to the muscles of mastication (e.g., masseter), not the muscles of facial expression. * **Buccal branch:** Supplies the buccinator and muscles of the upper lip; injury would affect cheek tension and the ability to whistle or pucker. **High-Yield NEET-PG Pearls:** * **Pes Anserinus:** The "goose's foot" pattern formed by the branching of the facial nerve within the parotid gland. * **Safe Plane:** During parotidectomy, the facial nerve is the critical landmark that divides the gland into superficial and deep lobes. * **Most common nerve injured:** The marginal mandibular nerve is particularly vulnerable because it often dips below the lower border of the mandible before ascending to the lip.

Q: After extraction of the 3rd molar, paraesthesia occurs over the chin. This is due to the involvement of which nerve?

Inferior alveolar nerve.. The extraction of a mandibular third molar (wisdom tooth) is a common surgical procedure that carries a risk of nerve injury due to the close anatomical proximity of specific branches of the mandibular nerve ($V_3$). ### Why Option A is Correct The **Inferior Alveolar Nerve (IAN)** runs within the mandibular canal, which is located immediately inferior to the roots of the third molar. During extraction, the nerve can be compressed or damaged. The IAN eventually exits the **mental foramen** (near the premolars) as the **mental nerve**. The mental nerve provides sensory innervation to the **skin of the chin**, the lower lip, and the labial gingiva. Therefore, damage to the IAN results in paresthesia (numbness or tingling) over the chin. ### Why Other Options are Incorrect * **B. Lingual Nerve:** This nerve lies on the lingual (tongue) side of the third molar. Injury to this nerve would cause loss of sensation and taste to the **anterior 2/3 of the tongue** and the floor of the mouth, but not the skin of the chin. * **C. Buccal Nerve:** This nerve provides sensory innervation to the **cheek** (buccal mucosa). It does not supply the chin. * **D. All of the above:** Incorrect because the sensory distribution of the lingual and buccal nerves does not include the mental region. ### High-Yield Clinical Pearls for NEET-PG * **Mental Nerve:** It is the terminal branch of the IAN. Remember: **IAN $\rightarrow$ Mental Nerve $\rightarrow$ Chin/Lower Lip.** * **Radiographic Sign:** On an OPG (Orthopantomogram), if the mandibular canal is diverted or the roots of the 3rd molar appear darkened/nicked, there is a high risk of IAN injury. * **Nerve most commonly injured:** While IAN injury is common, the **Lingual nerve** is also frequently at risk during the surgical flap reflection for 3rd molar surgery. Always distinguish between "numbness of the tongue" (Lingual) vs. "numbness of the chin" (IAN).

Q: What is the distance of the promontory from the tympanic membrane?

2 mm. The **middle ear (tympanic cavity)** is a narrow, air-filled space shaped like a biconcave disc [1]. Its narrowest dimension is the distance between the lateral wall (tympanic membrane) and the medial wall (labyrinthine wall). 1. **Why 2 mm is correct:** The medial wall of the middle ear features a rounded projection called the **promontory**, which is formed by the basal turn of the cochlea. Because the tympanic membrane is "tented" inwards (at the umbo), the distance between the umbo and the promontory is the narrowest part of the cavity, measuring approximately **2 mm**. 2. **Why other options are wrong:** * **5 mm:** This is the approximate distance at the floor (hypotympanum) of the middle ear. * **6 mm:** This represents the vertical and anteroposterior diameters of the tympanic cavity, but not the width. * **7 mm:** This is the approximate distance at the roof (epitympanum) of the middle ear. **High-Yield NEET-PG Pearls:** * **Dimensions of the Middle Ear:** Remember the "2-4-6" rule for the width of the cavity: 2 mm at the center (level of the promontory), 4 mm at the floor, and 6 mm at the roof. * **Promontory:** It is covered by the **tympanic plexus** (formed by the tympanic branch of the Glossopharyngeal nerve, CN IX). * **Clinical Significance:** In cases of **Glomus Jugulare** or **Glomus Tympanicum**, a "red flush" may be seen behind the tympanic membrane over the promontory (Rising Sun sign). * **Anatomy:** The promontory lies between the **fenestra vestibuli** (oval window) above and the **fenestra cochleae** (round window) below and behind.

Q: Retroauricular incision in children less than 2 years old may cause damage to which cranial nerve?

VII. The correct answer is **VII (Facial Nerve)**. **Why it is correct:** In infants and children under 2 years of age, the **mastoid process** is not yet developed (it begins developing around the end of the first year and matures by age 2). Consequently, the **stylomastoid foramen**, through which the Facial Nerve (CN VII) exits the skull, is located very superficially and laterally on the skull base. In adults, the mastoid process provides a bony "shield" that protects the nerve. In young children, a retroauricular (behind the ear) incision can easily transect the nerve because it lies just beneath the skin and fascia, lacking this bony protection. **Why the other options are incorrect:** * **A (VIII - Vestibulocochlear):** This nerve remains deep within the internal acoustic meatus and the petrous part of the temporal bone. It is not at risk during superficial skin incisions. * **C (VI - Abducens):** This nerve has a long intracranial course and exits via the superior orbital fissure to supply the lateral rectus muscle. It is nowhere near the retroauricular region. * **D (V - Trigeminal):** While the Trigeminal nerve provides sensory innervation to the face, the specific risk in this surgical approach is the motor trunk of the Facial nerve. The Great Auricular nerve (C2, C3) provides sensation to this area, not CN V. **High-Yield NEET-PG Pearls:** * **Developmental Milestone:** The mastoid process develops due to the pull of the **Sternocleidomastoid muscle** as the child begins to hold their head up and move. * **Surgical Safety:** To avoid CN VII injury in infants, incisions should be placed more superiorly or further away from the anticipated exit point of the stylomastoid foramen. * **Other superficial structures:** The **Parotid gland** is also more superiorly placed in neonates, further exposing the facial nerve branches.

Q: Which of the following statements about the inferior oblique muscle is false?

It originates from the annulus of Zinn.. The **Inferior Oblique (IO)** is unique among the extraocular muscles because it is the only one that does not originate from the common tendinous ring (Annulus of Zinn) at the apex of the orbit. Instead, it originates from the **orbital surface of the maxilla**, just lateral to the lacrimal groove. This makes Option C the false statement and the correct answer. **Analysis of Options:** * **Option A (Shortest muscle):** This is a true statement. The inferior oblique is the shortest extraocular muscle (approx. 37 mm), while the superior oblique is the longest. * **Option B (Supplied by 3rd CN):** This is true. The IO is supplied by the **inferior division of the Oculomotor nerve (CN III)**. Note: The nerve to the IO also carries parasympathetic fibers to the ciliary ganglion. * **Option D (Primary action is extorsion):** This is true. Due to its insertion behind the equator on the postero-lateral aspect of the globe, its primary action is **extorsion**. Its secondary action is elevation and tertiary action is abduction [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Origin Rule:** All recti originate from the Annulus of Zinn. Both obliques are "outliers"—the Superior Oblique originates from the sphenoid bone (above the annulus), and the Inferior Oblique originates from the floor of the orbit. * **Mnemonic for Nerve Supply:** **LR6SO4EE3** (Lateral Rectus-CN6; Superior Oblique-CN4; Everything Else-CN3). * **Testing Position:** To isolate the action of the Inferior Oblique clinically, the patient is asked to look **inward (adduction) and then upward**.

Question 1

What is the relationship of the artery, vein, and nerve within the parotid gland from lateral to medial?

Accepted Answer

Nerve, Vein, Artery

Answer

Artery, Vein, Nerve

Answer

Vein, Artery, Nerve

Answer

Vein, Nerve, Artery

Question 2

Which branch of the angular vein causes cavernous sinus thrombosis?

Accepted Answer

Supraorbital vein

Answer

Maxillary vein

Answer

Infraorbital vein

Answer

Supratrochlear vein

Question 3

Which of the following muscles is NOT an elevator of the mandible?

Accepted Answer

Digastric

Answer

Temporalis

Answer

Medial pterygoid

Answer

Masseter

Question 4

An 8-year-old boy had an extensive mastoidectomy due to an infection that did not respond to antibiotics. Postoperatively, he developed Bell's palsy (facial paralysis). A feature of this paralysis was the accumulation of saliva in the oral vestibule, leading to dribbling from the corner of his mouth. Which of the following muscles was paralyzed, causing this specific symptom?

Accepted Answer

Buccinator

Answer

Zygomaticus major

Answer

Orbicularis oculi

Answer

Levator palpebrae superioris

Question 5

A 55-year-old woman has undergone facial surgery for the excision of a malignant parotid tumor. A week postoperatively, marked weakness is seen in the musculature of the patient's lower lip. Which of the following nerves was most likely injured during the parotidectomy?

Accepted Answer

Marginal mandibular branch of facial

Answer

Zygomatic branch of facial

Answer

Mandibular division of the trigeminal nerve

Answer

Buccal branch of facial

Question 6

After extraction of the 3rd molar, paraesthesia occurs over the chin. This is due to the involvement of which nerve?

Accepted Answer

Inferior alveolar nerve.

Answer

Lingual nerve.

Answer

Buccal nerve.

Answer

All of the above.

Question 7

What is the distance of the promontory from the tympanic membrane?

Accepted Answer

2 mm

Answer

5 mm

Answer

6 mm

Answer

7 mm

Question 8

Retroauricular incision in children less than 2 years old may cause damage to which cranial nerve?

Accepted Answer

VII

Answer

VIII

Answer

VI

Answer

V

Question 9

Which of the following anatomical structures is not present at the petrous part of the temporal bone?

Accepted Answer

Mastoid tip

Answer

Mastoid antrum

Answer

Ethmoidal labyrinth

Answer

Endolymphatic sinus

Question 10

Which of the following statements about the inferior oblique muscle is false?

Accepted Answer

It originates from the annulus of Zinn.

Answer

It is the shortest muscle.

Answer

It is supplied by the 3rd cranial nerve.

Answer

Its primary action is extorsion.

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