Cranial nerves > FACIAL NERVE > Flashcards

FACIAL NERVE Flashcards

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1
Q

🧠 What is the facial nerve (CN VII) in one simple sentence?

A

The facial nerve is a mixed cranial nerve that controls facial expression 😃, supplies taste to the anterior tongue 👅, and carries parasympathetic fibres to glands 💧🌿.

🧠 Key idea:
Face movement + taste + tears + saliva.

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2
Q

🧠 Why does the facial nerve have MULTIPLE nuclei?

A

Because CN VII carries different fibre types, each requiring a different nucleus:
• Motor 💪 (muscles)
• Parasympathetic 🌿 (glands)
• Sensory (taste) 👅
• Somatic sensory 👂 (ear)

🧠 Different jobs → different nuclei.

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3
Q

🧠 How many nuclei are associated with the facial nerve?

A

👉 FOUR nuclei 🔢

🔥 Exam pearl 🔥
CN VII has 4 nuclei, spread across the pons & medulla 🧠.

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4
Q

🧠 What are the FOUR nuclei of the facial nerve?

A

1️⃣ Facial motor nucleus 💪
2️⃣ Superior salivatory nucleus 🌿
3️⃣ Nucleus solitarius 👅
4️⃣ Spinal trigeminal nucleus 👂

🧠 Each nucleus matches one fibre type.

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5
Q

🧠 Which nucleus provides MOTOR fibres for CN VII?

A

👉 Facial motor nucleus 💪

🧠 Fibre type:
• Branchial motor (SVE)

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6
Q

🧠 Where is the facial motor nucleus located EXACTLY?

A

Located:
• 🧠 In the pons
• 📍 Caudal (lower) pons
• 📍 Ventral (anterior) to the fourth ventricle
• 📍 Medial in the brainstem

🧠 Rule:
Motor nuclei are medial.

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7
Q

🧠 What IMPORTANT anatomical structure is formed by facial nerve fibres in the pons?

A

👉 Facial colliculus 🔥

🧠 Formed because:
• CN VII fibres loop around the abducens nucleus (CN VI)

🔥 VERY HIGH-YIELD 🔥
Facial colliculus = CN VII fibres + CN VI nucleus.

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8
Q

🧠 What muscles are ultimately supplied by the facial motor nucleus?

A

• Muscles of facial expression 😃
• Stapedius 🔊
• Stylohyoid
• Posterior belly of digastric

🧠 All facial movement starts here.

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9
Q

🧠 Which nucleus provides PARASYMPATHETIC fibres for CN VII?

A

👉 Superior salivatory nucleus 🌿

🧠 Fibre type:
• Preganglionic parasympathetic (GVE)

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10
Q

🧠 Where is the superior salivatory nucleus located?

A

Located:
• 🧠 In the pons
• 📍 Close to facial motor nucleus
• 📍 Dorsal and slightly medial

🧠 Often remembered together.

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11
Q

🧠 What glands are controlled by parasympathetic fibres from CN VII?

A

• Lacrimal gland 💧 (tears)
• Submandibular gland 💧 (saliva)
• Sublingual gland 💧 (saliva)
• Nasal & palatine glands

🧠 Think: tears + saliva.

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12
Q

🧠 Which nucleus receives TASTE fibres from the facial nerve?

A

👉 Nucleus solitarius 👅

🧠 Fibre type:
• Special visceral afferent (SVA)

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13
Q

🧠 Where is the nucleus solitarius located?

A

Located:
• 🧠 In the medulla
• 📍 Dorsal medulla
• 📍 Near the floor of the fourth ventricle

🧠 Shared by CN VII, IX, X.

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14
Q

🧠 What taste area does CN VII supply?

A

👉 Anterior two-thirds of the tongue 👅

⚠️ Taste only — NOT general sensation.

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15
Q

🧠 Which nucleus receives SOMATIC SENSORY input from CN VII?

A

👉 Spinal trigeminal nucleus 👂

🧠 Fibre type:
• General somatic afferent (GSA)

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16
Q

🧠 What sensory information from CN VII goes to the spinal trigeminal nucleus?

A

• External auditory canal
• Part of tympanic membrane
• Area around the ear

🧠 Small but exam-relevant.

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17
Q

🧠 From which part of the brainstem does the facial nerve emerge?

A

👉 From the pons 🧠

📍 Specifically:
• Pontomedullary junction
• Near CN VIII

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18
Q

🧠 What TWO roots does the facial nerve emerge as?

A

1️⃣ Motor root
2️⃣ Nervus intermedius

🧠 Nervus intermedius carries:
• Parasympathetic fibres 🌿
• Taste fibres 👅
• Somatic sensory fibres

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19
Q

🧠 Which nuclei contribute fibres to the nervus intermedius?

A

• Superior salivatory nucleus
• Nucleus solitarius
• Spinal trigeminal nucleus

🧠 Facial motor nucleus does NOT contribute.

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20
Q

🧠 One-line MASTER EXAM SUMMARY (nuclei & origin)?

A

The facial nerve originates in the pons and is associated with four nuclei: the facial motor nucleus (facial expression), superior salivatory nucleus (parasympathetic to lacrimal and salivary glands), nucleus solitarius (taste from anterior two-thirds of tongue), and spinal trigeminal nucleus (somatic sensory from the ear).

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21
Q

🧠 What does “CN VII course from brainstem → face” mean?

A

It means tracking CN VII physically 🧭:
• Pons exit
• Internal acoustic meatus
• Facial canal
• Middle ear region
• Stylomastoid foramen
• Parotid gland
• Facial muscles

🧠 And following branching fibre types.

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22
Q

🧠 Where does CN VII emerge from the brainstem?

A

At the:
• Pontomedullary junction
• Cerebellopontine angle
• Near CN VIII

🧠 Emerges as two parts.

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23
Q

🧠 What are the TWO roots of CN VII at brainstem exit?

A

1️⃣ Motor root 💪 → facial expression
2️⃣ Nervus intermedius 🌿👅 → parasympathetic, taste, sensory

🧠 Exam phrase:
Motor root + nervus intermedius.

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24
Q

🧠 What is the FIRST major tunnel CN VII enters?

A

👉 Internal acoustic meatus 🕳️

📍 In the petrous temporal bone
🧠 Entered with CN VIII.

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25
**🧠 What is the internal acoustic meatus?**
A **bony canal** in the temporal bone that transmits nerves from the **posterior cranial fossa** into the temporal bone. 🧠 Think: **doorway into the temporal bone** 🚪.
26
**🧠 After the internal acoustic meatus, where does CN VII go?**
👉 Into the **facial canal (Fallopian canal)** 🦴 📍 Inside the **petrous temporal bone** 🧠 Long intrabony course.
27
**🧠 What is the facial canal?**
A **bony passageway** carrying CN VII from the **internal acoustic meatus** to the **stylomastoid foramen**. 🧠 Explains vulnerability to **compression**.
28
**🧠 What is the FIRST bend of CN VII inside the facial canal?**
👉 **Geniculate bend (genu)** 🔄 🧠 A sharp **knee-like bend**.
29
**🧠 What is the geniculate ganglion?**
A **sensory ganglion** of CN VII containing cell bodies for: • **Taste fibres** 👅 • **Small ear sensation** ⚠️ **NOT motor**.
30
**🧠 What major branch leaves CN VII at the geniculate ganglion?**
👉 **Greater petrosal nerve** 🌿 Carries **preganglionic parasympathetic fibres** to: • **Lacrimal** • **Nasal & palatal glands** (via pterygopalatine ganglion).
31
**🧠 After the geniculate ganglion, what is the direction of CN VII?**
It continues: • **Posteriorly** • Then **inferiorly** 🧠 A curved intratemporal path.
32
**🧠 What branch to the middle ear leaves CN VII in the facial canal?**
👉 **Nerve to stapedius** 🔊 🧠 Dampens loud sounds.
33
**🧠 Where does the chorda tympani arise and what does it do?**
Arises from the **lower facial canal**, enters the **middle ear**, passes through the **tympanic cavity**, and exits to join **V3** in the infratemporal fossa.
34
**🧠 What fibres travel in the chorda tympani?**
• **Taste** from anterior **⅔ of tongue** 👅 • **Preganglionic parasympathetic fibres** 🌿 to: – **Submandibular gland** – **Sublingual gland**
35
**🧠 How does CN VII leave the skull?**
👉 Via the **stylomastoid foramen** 🕳️ 📍 Between **styloid** and **mastoid** processes.
36
**🧠 What happens immediately after CN VII exits the stylomastoid foramen?**
It gives motor branches: • **Posterior auricular** • **Stylohyoid** • **Posterior belly of digastric** 🧠 BEFORE entering parotid gland.
37
What does the posterior auricular nerve supply?
***It supplies:*** 🦻** Auricular muscles (ear movement) 🧑‍🦲 **Occipitalis muscle (scalp)** Very simply: **Auricular muscles → tiny ear movements** **Occipitalis → pulls the scalp backwards** 🧠 In humans: Function is minor But important for localisation
38
What does the stylohyoid muscle do?
The stylohyoid muscle: **Elevates the hyoid bone **Pulls it backwards** 🧠 Why this matters: Elevating the hyoid helps swallowing
39
Why is the stylohyoid muscle important clinically?
Because: It stabilises the throat during swallowing Weakness can subtly affect swallowing coordination 🧠 Supplied by CN VII only
40
What is special about the digastric muscle?
It has TWO bellies with different nerve supplies: Anterior belly → CN V3 Posterior belly → CN VII
41
What does the posterior belly of digastric do?
It does TWO things: 1️⃣** Elevates the hyoid bone 2️⃣ Helps open the mouth (depresses mandible when hyoid fixed)** 🧠 Important for: Swallowing Speech Chewing coordination
42
Why does CN VII supply swallowing-related muscles?
Because CN VII is a branchial motor nerve. 🧠 It supplies muscles derived from the second pharyngeal arch, including: Stylohyoid Posterior belly of digastric
43
Q️⃣ What is the stylohyoid branch, and what does the stylohyoid muscle do?
he stylohyoid branch of CN VII supplies the stylohyoid muscle. 📍 Stylohyoid muscle: Runs from the styloid process → hyoid bone 🧠 Function (very simply): Elevates and retracts the hyoid bone Helps initiate swallowing 🧠 Why this matters: Elevating the hyoid helps lift the larynx during swallowing 🔥 Exam pearl: Stylohyoid = supports swallowing
44
**🧠 Does CN VII innervate the parotid gland?**
❌ **NO** 🧠 CN VII **passes through** parotid but **does not innervate it**. 👉 Parotid parasympathetic supply = **CN IX**.
45
**🧠 What is the parotid plexus?**
A **branching network** of CN VII within the parotid gland called the **pes anserinus**, organising terminal motor branches.
46
**🧠 What are the FIVE terminal branches of CN VII?**
1️⃣ **Temporal** 2️⃣ **Zygomatic** 3️⃣ **Buccal** 4️⃣ **Marginal mandibular** 5️⃣ **Cervical** 🧠 Mnemonic: **To Zanzibar By Motor Car** 🚗
47
**🧠 What do the terminal branches of CN VII do?**
They deliver **motor fibres** 💪 to the **muscles of facial expression**.
48
**🧠 One-line MASTER EXAM SUMMARY (course)?**
The facial nerve exits the pons as a **motor root and nervus intermedius**, enters the **internal acoustic meatus**, traverses the **facial canal** giving off the **greater petrosal nerve**, **nerve to stapedius**, and **chorda tympani**, exits via the **stylomastoid foramen**, then passes through the **parotid gland** to form the **parotid plexus** and its **five terminal branches** supplying muscles of facial expression.
49
**🧠 What functions can be affected in a facial nerve (CN VII) lesion?**
CN VII lesions can affect **FOUR key functions** 🔢: 1️⃣ **Facial expression** 😃 (motor) 2️⃣ **Taste** 👅 (anterior **⅔ of tongue**) 3️⃣ **Lacrimation & salivation** 💧🌿 (parasympathetic) 4️⃣ **Hearing modulation** 🔊 (**stapedius muscle**) 🧠 The **COMBINATION** of deficits tells you **WHERE** the lesion is.
50
**🧠 What is the MOST IMPORTANT first step in localising a CN VII lesion?**
👉 Decide whether the lesion is: • **UMN (central)** 🧠 or • **LMN (peripheral)** 😐 🔥 This is the **SINGLE MOST TESTED CONCEPT**.
51
**🧠 What is an UMN facial nerve lesion?**
An **upper motor neuron (UMN)** lesion affects: • The **corticobulbar pathway** • **ABOVE** the **facial motor nucleus** in the pons 🧠 The **facial nerve itself is intact**.
52
**🧠 What is an LMN facial nerve lesion?**
A **lower motor neuron (LMN)** lesion affects: • The **facial nerve nucleus** • OR the **facial nerve after it leaves the brainstem** 🧠 This directly damages the nerve supplying the face.
53
**🧠 Why does the FOREHEAD matter so much in facial nerve lesions?**
Because the **upper face (forehead)** receives: 👉 **BILATERAL cortical innervation** 🔁 🧠 The **lower face** receives **ONLY contralateral input**. 🔥 This explains **UMN vs LMN** differences.
54
**🧠 What happens to the FOREHEAD in an UMN facial nerve lesion?**
👉 **FOREHEAD IS SPARED** ✅ • Patient can **wrinkle forehead** • But cannot **smile** on the affected side 🧠 Classic exam phrase: **Forehead sparing = UMN lesion**.
55
**🧠 What happens to the FOREHEAD in an LMN facial nerve lesion?**
👉 **FOREHEAD IS AFFECTED** ❌ • Cannot wrinkle forehead • Cannot close eye • Cannot smile on that side 🧠 **Whole half of face** is weak.
56
**🧠 What are the key features of an UMN facial nerve lesion?**
• **Contralateral lower facial weakness** • **Forehead spared** ✅ • Eye closure preserved 👁️ • **No taste or lacrimation loss** 🧠 Think: **STROKE** 🧠⚡
57
**🧠 What is the most common cause of UMN facial nerve palsy?**
👉 **STROKE** 🧠⚡ • Cortical • Internal capsule 🧠 Often with: • Arm/leg weakness • Speech disturbance
58
**🧠 What are the key features of an LMN facial nerve lesion?**
• **Ipsilateral upper + lower facial weakness** • Cannot wrinkle forehead ❌ • Cannot close eye ❌ • Flattened nasolabial fold 🧠 Entire half of face affected.
59
**🧠 What is the MOST COMMON cause of LMN facial nerve palsy?**
👉 **BELL’S PALSY** 🔥 🧠 Extremely **high-yield**.
60
**🧠 What is Bell’s palsy?**
Bell’s palsy is an **acute, idiopathic LMN facial nerve palsy**, due to **inflammation and oedema** of **CN VII**. 🧠 Often linked to **viral reactivation (HSV)** 🦠.
61
**🧠 Where is the facial nerve damaged in Bell’s palsy?**
👉 Inside the **FACIAL CANAL** 🦴 (temporal bone) 🧠 Tight bony canal → **compression when swollen**.
62
**🧠 What are the classic features of Bell’s palsy?**
• **Sudden onset** (hours–days) • Entire half of face weak • **Forehead involved** • Inability to close eye 👁️❌ • Mouth droops 😐 🧠 **NO other neurological deficits**.
63
**🧠 Is Bell’s palsy UMN or LMN?**
👉 **LMN LESION** ❗ 🧠 Frequently directly asked.
64
**🧠 What does HYPERACUSIS mean?**
👉 **Sounds seem abnormally loud** 🔊❗ 🧠 Due to loss of sound dampening.
65
**🧠 Why does hyperacusis occur in facial nerve lesions?**
Because CN VII supplies the **STAPEDIUS muscle**: • Stapedius normally **dampens loud sounds** • Lesion → **stapedius paralysis** • Result → **hyperacusis** 🔊
66
**🧠 What does hyperacusis tell you about lesion location?**
👉 Lesion is **PROXIMAL to the nerve to stapedius** 📍 i.e. **INSIDE the facial canal** 🦴 🧠 Key localisation clue.
67
**🧠 What causes LOSS OF TASTE in facial nerve lesions?**
Damage to the **CHORDA TYMPANI** 👅: • Carries **taste from anterior ⅔ of tongue** • Carries parasympathetic fibres to salivary glands
68
**🧠 What does loss of taste tell you about lesion location?**
👉 Lesion is **PROXIMAL to chorda tympani origin** 📍 **Inside facial canal**, above chorda tympani.
69
**🧠 What causes DRY EYE in facial nerve lesions?**
Damage to parasympathetic fibres to the **LACRIMAL GLAND** 💧 🧠 These travel via: • **Greater petrosal nerve** • From **superior salivatory nucleus**
70
**🧠 What does dry eye tell you about lesion location?**
👉 Lesion is **PROXIMAL to the GENICULATE GANGLION** 🔥 🧠 Indicates a **VERY proximal lesion**.
71
**🧠 If facial weakness occurs WITHOUT hyperacusis or taste loss, where is the lesion?**
👉 **DISTAL to chorda tympani & nerve to stapedius** 📍 Likely **AFTER stylomastoid foramen** 🧠 **Pure motor lesion**.
72
**🧠 If facial weakness + hyperacusis + taste loss are present, where is the lesion?**
👉 **WITHIN the facial canal**, proximal to both branches 🧠 Classic for **BELL’S PALSY** 🔥.
73
**🧠 If facial weakness + dry eye are present, where is the lesion?**
👉 **VERY PROXIMAL lesion** 📍 At or **before the geniculate ganglion** 🧠 Parasympathetic fibres affected early.
74
**🧠 Can you summarise CN VII lesion localisation in one logical flow?**
• **Forehead spared** → **UMN lesion** • **Forehead involved** → **LMN lesion** • **Hyperacusis** → above nerve to stapedius • **Taste loss** → above chorda tympani • **Dry eye** → above geniculate ganglion 🧠 **Stack features to pinpoint location** 📍.
75
**🧠 One-line MASTER EXAM SUMMARY?**
**Facial nerve lesions are localised by distinguishing UMN lesions**, which spare the **forehead** due to **bilateral cortical innervation**, from **LMN lesions**, which affect the **entire ipsilateral face**; additional features such as **hyperacusis**, **loss of taste from the anterior tongue**, and **reduced lacrimation** indicate progressively **more proximal lesions** along CN VII, classically seen in **Bell’s palsy**.
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