Neurological Examination

Cranial Nerves I–XII

Exam techniques, peripheral vs central lesion patterns, brainstem syndromes, and the clinical pearls that distinguish benign from dangerous presentations.

Clinical Presets

Select Nerve

VII

Facial

mixedpons
Exit: Internal acoustic meatus → stylomastoid foramenNuclei: Facial motor nucleus (pons), Superior salivatory nucleus (parasympathetic), Nucleus of solitary tract (taste)

Functions

  • Facial expression muscles (frontalis, orbicularis oculi, orbicularis oris, etc.)
  • Taste: anterior 2/3 of tongue (via chorda tympani)
  • Lacrimation and salivation (submandibular, sublingual glands)
  • Stapedius muscle (dampens loud sounds)

Exam Technique

  • Raise eyebrows (frontalis) — KEY UMN vs. LMN test
  • Close eyes tightly (orbicularis oculi) — test strength
  • Smile / show teeth (orbicularis oris, zygomaticus)
  • Puff cheeks
  • Taste testing if indicated (sweet/salty/sour on anterior tongue)

Normal: Symmetric facial movements including forehead, full eye closure, symmetric smile

Peripheral Lesion

LMN facial palsy (Bell's palsy pattern)

  • ENTIRE HALF OF FACE weak (forehead INCLUDED)
  • Cannot wrinkle forehead on affected side
  • Incomplete eye closure (lagophthalmos) — risk of corneal exposure
  • May have: hyperacusis (stapedius), loss of taste anterior 2/3 tongue, dry eye

LMN damage affects all ipsilateral facial muscles because all fibers converge in one nerve trunk

Common causes

  • Bell's palsy (idiopathic, likely HSV reactivation — most common cause)
  • Ramsay Hunt syndrome (VZV — vesicles in ear canal, worse prognosis)
  • CPA tumor (acoustic neuroma — gradual onset, not sudden)
  • Lyme disease (can be bilateral!)
  • Parotid tumor or surgery

Central Lesion

UMN facial palsy (supranuclear)

  • LOWER FACE ONLY weak (forehead SPARED)
  • Can still wrinkle forehead and close eyes
  • Emotional facial movements may be preserved (or vice versa — dissociation)

Upper face receives BILATERAL corticobulbar input; lower face receives only CONTRALATERAL input

Common causes

  • Stroke (MCA territory)
  • Mass lesion
  • Forehead sparing is the key — distinguishes from Bell's palsy

Clinical Pearls

  • FOREHEAD SPARING = UMN = stroke workup. FOREHEAD INVOLVED = LMN = Bell's palsy workup. This is the #1 CN exam distinction.
  • Bell's palsy is a diagnosis of EXCLUSION — check for vesicles (Ramsay Hunt), bilateral involvement (Lyme, GBS, sarcoid), and gradual onset (tumor)
  • Eye protection is critical in LMN palsy — inability to close the eye causes corneal desiccation