A 17-year-old girl presents to an urgent care clinic after waking up in the morning with a left-sided facial droop and an inability to fully close her left eye. Of note, she is currently on oral contraceptives and escitalopram and smokes half a pack of cigarettes per day. Her temperature is 98.2°F (36.8°C), blood pressure is 110/68 mmHg, pulse is 82/min, and respirations are 12/min. On exam, she has generalized, unilateral left-sided drooping of her upper and lower face, and an inability to move the left side of her mouth or close her left eye. Her extraocular movements and swallow are intact. She has no other neurologic deficits. Which of the following interventions would most likely address the most likely cause of this patient's symptoms?

Implantation of gold weight for eyelid

A 63-year-old man is brought to the emergency department by his wife because she is concerned he is having another stroke. The patient says he woke up with right-sided facial weakness and drooping. Past medical history is significant for a recent case of shingles treated with acyclovir, and a stroke, diagnosed 10 years ago, from which he recovered with no residual functional deficits. On physical examination, there is weakness and drooping of the entire right side of the face. Sensation is intact. The remainder of the physical examination is unremarkable. Which of the following additional findings would also most likely be seen in this patient?

Complete loss of taste to the tongue

A 65-year-old man presents with facial weakness. He says he noticed that his face appeared twisted when he looked in the bathroom mirror this morning. He is otherwise well and does not have any other complaints. He denies any facial pain or paresthesia. No significant past medical history. The patient is afebrile and vital signs are within normal limits. Neurological examination reveals difficulty shutting the right eye tight and inability to bring up the right corner of his mouth when asked to smile. Remainder of the exam, including the left side of the face, is unremarkable. Which of the following is the most likely diagnosis in this patient?

Left middle cerebral artery stroke

A 24-year-old man is brought to the emergency department 30 minutes after being involved in a high-speed motor vehicle collision in which he was a restrained driver. On arrival, he is alert and oriented. His pulse is 112/min, respirations are 29/min, and blood pressure is 100/60 mm Hg. The pupils are equal and reactive to light. There is a 3-cm laceration over the forehead and multiple bruises over the trunk. The lungs are clear to auscultation. Cardiac examination shows no abnormalities. The abdomen is soft and nontender. The right knee is swollen and tender; range of motion is limited by pain. Infusion of 0.9% saline is begun and intravenous acetaminophen is administered. Two hours later, blood-tinged fluid spontaneously drains from both nostrils, and is made worse by leaning forward. On a piece of gauze, it shows up as a rapidly-expanding clear ring of fluid surrounding blood. Further evaluation of this patient is most likely to show which of the following?

Bilateral periorbital ecchymosis

Face and scalp for USMLE Step 2 CK: High-Yield Anatomy Lessons

Facial Nerves & Muscles - The Expression Controllers

Facial Nerve (CN VII): Chief motor supply to the muscles of facial expression. Exits the skull via the stylomastoid foramen before branching within the parotid gland.
- Five Terminal Branches: Temporal, Zygomatic, Buccal, Mandibular, Cervical.
- 📌 Mnemonic: To Zanzibar By Motor Car.

Facial Nerve Branches

Key Muscles & Actions:
- Frontalis: Raises eyebrows.
- Orbicularis Oculi: Closes eye; tested by asking patient to shut eyes tightly.
- Zygomaticus Major: Elevates corner of mouth (smiling).
- Orbicularis Oris: Closes and purses lips.
- Buccinator: Compresses cheek against teeth.
- Platysma: Tenses neck skin.
Clinical Pearl: Facial Nerve Palsy
- LMN Lesion (Bell's Palsy): Ipsilateral paralysis of the entire face. Forehead is not spared.

⭐ In an Upper Motor Neuron (UMN) lesion (e.g., stroke), the forehead is spared. This is due to bilateral cortical innervation to the upper face (frontalis muscle). The lower face will show contralateral paralysis.

Vascular Supply & Scalp - Plumbing and Protection

Arterial and nerve supply of the scalp

Arterial Supply: Rich anastomoses from two main sources:
- External Carotid Artery: Supplies most of the face via:
  - Facial Artery
  - Superficial Temporal Artery
  - Maxillary Artery
- Internal Carotid Artery: Supplies the forehead via the Ophthalmic Artery branches (Supraorbital & Supratrochlear).
Venous Drainage: Primarily via Facial Vein, which drains into the Internal Jugular Vein (IJV).

⭐ Danger Triangle of the Face: The facial vein is valveless and connects with the cavernous sinus via the ophthalmic veins. Infections from the nose or upper lip can spread intracranially, causing cavernous sinus thrombosis.

Scalp Layers:
- 📌 S.C.A.L.P.
- Skin
- Connective Tissue (Dense): Highly vascular. In lacerations, vessels held open by fibrous septa, causing profuse bleeding.
- Aponeurosis (Epicranial)
- Loose Areolar Tissue: "Danger Area"; allows spread of infection.
- Pericranium (Periosteum of skull)

Clinical Correlates - Facial Faults

Bell's Palsy (LMN Lesion):
- Idiopathic paralysis of the facial nerve (CN VII).
- Acute, unilateral weakness/paralysis of all facial expression muscles.
- Features: inability to wrinkle forehead, eyebrow sag, drooping eyelid, inability to smile on one side.
Trigeminal Neuralgia (Tic Douloureux):
- Excruciating, paroxysmal pain in CN V distribution (V2/V3 > V1).
- Triggered by touch, chewing, or cold.
Danger Triangle of the Face:
- Infections can spread via facial vein → ophthalmic veins → cavernous sinus, causing thrombosis.

⭐ In a central facial palsy (UMN lesion, e.g., stroke), forehead muscles are spared due to bilateral cortical innervation. In Bell's Palsy (LMN lesion), the entire ipsilateral face is paralyzed.

Facial Paralysis: UMN vs. LMN Lesions

High‑Yield Points - ⚡ Biggest Takeaways

Facial nerve (CN VII) innervates muscles of facial expression; its paralysis leads to Bell's palsy.

Trigeminal nerve (CN V) provides sensory supply to the face via its three divisions (V1, V2, V3).

The danger triangle of the face can drain infections to the cavernous sinus.

The scalp's 5 layers (S.C.A.L.P.) include the loose areolar tissue, the "danger area" for infection spread.

Bell's Palsy, a lower motor neuron lesion of CN VII, causes ipsilateral full-face paralysis.

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Face and scalp