Makindo Medical Notes.com

Related Subjects: |Cortical functions |Motor System |Sensory System |Mental state Examination |Speech and Language Exam |Cranial nerves and examination |Assessing Cognition

Brain Stem Anatomy/ Cranial nerves

The Brainstem contains all the cranial nerves other than Olfactory and optic nerves

CN I: Olfactory

• Test each nostril in turn with orange peel or coffee, vanilla, peppermint. Do not use smelling salts.
• Affected in meningioma, frontal tumour , An early sign in Parkinson’s disease and perhaps some dementias

CN II: Optic nerve (covered elsewhere)

• Visual acuity
: Use finger counting, newspaper print ideally a Snellen chart
• Visual fields
: by confrontation
• Pupil size
• Large:mydiasis
• Small: Miosis
• Pupil response to light
• Pupil response to accommodation
• Ophthalmoscopy
: look at retina

CN III, IV, VI: Oculomotor, Trochlear, Abducens - see eye section

• Look at pupils: shape, relative size, ptosis.
• Shine light in from the side to gauge pupil's light reaction.
• Assess both direct and consensual responses.
• Assess afferent pupillary defect by moving light in arc from pupil to pupil.
• Follow hand with eyes – placing a hand on head usually stops head moving. Do an H pattern.
• Look for failure of the movement, nystagmus [pause to check it during upward/ lateral gaze] and ask about diplopia
• Convergence by moving finger towards the bridge of pt's nose.
• Test accommodation by pt looking into the distance, then a finger 10cm from the nose.

CN V: Trigeminal

• Basics: Mixed sensory (face, gums, teeth, cornea, sinuses) and motor nerve (mastication muscles)
• Largest of the cranial nerves. Several brainstem nuclei.
• Examination: Corneal reflex: patient looks up and away as you touch the cornea with a wisp of cotton wool. Look for afferent blink (VII) reflex in both eyes, ask if could feel it.
• Facial sensation: sterile sharp item on forehead, cheek, jaw. Occiput and angle of jaw are supplied by C2. Repeat with a dull object. Ask to report sharp or dull. If abnormal, then temperature [heated/ water-cooled tuning fork], light touch [cotton].
• Motor: pt opens mouth, clenches teeth (pterygoids). Palpate temporal, masseter muscles as they clench. Test jaw jerk: Finger on tip of the jaw. Grip patellar hammer halfway up shaft and tap finger lightly. Usually, nothing happens, or just a slight closure. If increased closure, think UMNL, esp pseudobulbar palsy.
• Lesions seen with brainstem vascular disease, posterior fossa tumour s, herpes simplex and zoster infections, MS can cause neuralgia, Trigeminal neuralgia dealt with later on

CN VII: Facial

• Basics: Nucleus lies in the pons
• Examination: Inspect facial droop or asymmetry. Subtle weaknesses may not be apparent until tested. Loss of nasolabial fold on the affected side. Unable to close eye or attempts to close and eye elevates (Bell's sign).
• Facial expression muscles: pt looks up and wrinkles forehead. Examine wrinkling loss.
• Feel muscle strength by pushing down on each side [UMN preserved because of bilateral innervation].
• Pt shuts eyes tightly: Try to open, compare each side.
• Pt grins, ask patient to whistle, puff cheeks. Ask to close your mouth and try to move lips apart.
• Corneal Blink reflex already done. See CN V
• Causes: LMN - Bells palsy, parotid tumour , Herpes Zoster (Ramsay Hunt syndrome with vesicles in outer ear) UMN - Stroke, SOL

CN VIII: Vestibulocochlear

• Basics : Hearing, Balance
• Nucleus in the Pons
• Rub one hand's fingers with noise on one side, another hand noiselessly. Ask pt. which ear they hear you rubbing. Repeat with louder intensity, watching for abnormality.
• Weber's test: Lateralization. 512/ 1024 Hz [256 if deaf] vibrating fork on top of patients head/ forehead. "Where do you hear sound coming from?" Normal reply is midline.
• Rinne's test: Air vs. Bone Conduction: 512/ 1024 Hz [256 if deaf] vibrating fork on mastoid behind the ear. Ask when stop hearing it. When stop hearing it, move to the patients ear so can hear it. Normal: air conduction [ear] better than bone conduction [mastoid].
• If indicated, look at external auditory canals, eardrums.

CN IX, X: Glossopharyngeal, Vagus

• Basics: Both Lie in the medulla
• Examination Voice: hoarse or nasal. Pt. swallows, coughs (bovine cough: recurrent laryngeal). >
• Examine palate for uvular displacement. (unilateral lesion: uvula drawn to normal side).
• Pt says "Ah": symmetrical soft palate movement.
• Gag reflex [sensory IX, motor X]: Stimulate back of throat each side. Normal to gag each time.

CN XI: Accessory

• Basics: Lies in the medulla
• Examination: From behind, examine for trapezius atrophy, asymmetry.
• Pt. shrugs shoulders (trapezius).
• Pt. turns head against resistance: watch, palpate SCM on the opposite side.

CN XII: Hypoglossal

• Basics: Lies in the medial medulla
• Examination: Listen to articulation.
• Inspect tongue in mouth for wasting, fasciculation.
• Protrude tongue: unilateral deviates to the affected side.