Facial nerve (CN VII) palsy

•    Upper motor neuron (UMN) lesion

o    Forehead spared (bilateral cortical representation of frontalis).

o    Contralateral lower facial weakness.

o    Causes: stroke (internal capsule, cortical).

•    Lower motor neuron (LMN) lesion

o    Whole ipsilateral face affected including forehead.

o    Loss of corneal reflex (efferent limb).

o    Hyperacusis, taste disturbance (anterior 2/3 tongue via chorda tympani).

o    Causes:

    Bell’s palsy (idiopathic, HSV reactivation)

    Ramsay Hunt syndrome (VZV, vesicles in ear canal)

    Lyme disease (bilateral possible)

    Sarcoidosis

    Parotid tumors

Trigeminal neuralgia (CN V)

•    Paroxysmal, unilateral, severe stabbing pain in V2 or V3 distribution.

•    Triggered by light touch, chewing, wind, talking.

•    First-line Rx: carbamazepine.

•    Secondary causes: compression (e.g., vascular loop, cerebellopontine angle tumor), MS (esp. bilateral cases).

Vestibulocochlear nerve (CN VIII)

•    Vestibular neuritis

o    Acute vertigo, nausea, gait unsteadiness.

o    No hearing loss.

o    Usually viral or post-viral.

•    Labyrinthitis

o    Vertigo with hearing loss ± tinnitus.

o    Often follows URTI.

•    Acoustic neuroma (vestibular schwannoma)

o    Progressive hearing loss, tinnitus, imbalance.

o    Can affect adjacent CN V (reduced corneal reflex) and CN VII (facial weakness).

Lateral medullary (Wallenberg) syndrome

•    PICA infarct, vertebral artery occlusion.

•    Features:

o    Vertigo, nausea, nystagmus.

o    Dysphagia, hoarseness (nucleus ambiguus).

o    Ipsilateral Horner’s syndrome.

o    Ipsilateral ataxia (cerebellar connections).

o    Ipsilateral facial sensory loss (pain/temp).

o    Contralateral loss of pain/temp in body (spinothalamic tract).

Other cranial nerve palsies

•    CN III palsy: pupil-involving (compressive, e.g., aneurysm), pupil-sparing (microvascular, e.g., diabetes).

•    CN IV palsy: vertical diplopia, worse on looking down (e.g., going downstairs).

•    CN VI palsy: horizontal diplopia, impaired abduction; raised ICP commonly stretches nerve.

•    CN IX, X palsy: dysphagia, hoarseness, reduced gag reflex.

•    CN XII palsy: tongue deviates toward lesion (LMN).

•    Common causes:

o    Diabetes (microvascular ischemia).

o    Trauma (base of skull fractures).

o    Raised ICP (uncal herniation → CN III).

o    Inflammatory (sarcoidosis).

o    Infections (e.g., Lyme disease).

Extra Revision Pearls

•    UMN vs LMN face clue: "Forehead spared → think stroke (UMN)."

•    Bilateral facial palsy clue → think Lyme disease, sarcoid, GBS.

•    Wallenberg clue → crossed sensory loss, Horner’s.

•    CN VI most susceptible to raised ICP (long intracranial course).

•    Acoustic neuroma clue → gradual hearing loss + imbalance + reduced corneal reflex.