Which of the following is correct when we assess for the first cranial nerve.
The cranial nerve examination is a complex mix of examination techniques designed to localise pathology to one or more of the twelve cranial nerves. Show
First StepsBefore commencing the cranial nerve exam, wash your hands, introduce yourself to the patient and gain consent. Position the patient comfortably, in a sitting position. Sit directly across from the patient with your eyes level with theirs. The Patient
Look at the patient, assessing for general comfort, any scars present around the face, and their general posture.
I - SmellThe olfactory nerve (cranial nerve I) provides olfactory sensation. The Olfactory Nerve (I) This nerve is not commonly assessed in detail, however a screening test can be performed by asking the patient to smell and identify a common scent (such as alcohol wipe, coffee or cinnamon). While loss of smell sensation - or anosmia - may be a sign of an olfactory nerve lesion, Parkinson’s disease is an important differential to keep in mind. II - VisionThe optic nerve (cranial nerve II) provides special sensory innervation, in the form of sight. The Optic Nerve (II)
II & III - PupilsThe optic nerve (II) provides the sensory pathway of the pupillary reflexes, interfacing with the Edinger-Westphal nucleus within the midbrain, with the oculomotor nerve (III) providing the motor pathway.
III, IV & VI - Eye MovementEye movement is innervated by the oculomotor (III), trochlear (IV) and abducens (VI) nerves. The Oculomotor Nerve (III) The Trochlear Nerve (IV) The Abducens Nerve (VI)
Nystagmus that is transient with onset following change in position is suggestive of benign paroxysmal positional vertigo, while vertical or torsional nystagmus are suggestive of a central cause.
The patient may also have fatiguability of eye movements, meaning that they can initially look up but not maintain this gaze over time - this is a sign of myaesthenia gravis. V - Facial Sensation & Jaw MusclesThe trigeminal nerve (V) innervates sensation of the face, corneas, nasal cavity and oral cavity. The third branch of the trigeminal nerve (the mandibular nerve) also innervates the muscles of mastication. The Trigeminal Nerve (V)
VII - Facial MovementThe facial nerve (VII) provides somatic motor supply for facial expression; somatic sensory supply to the external ear; taste to the anterior â…” of the tongue; and parasympathetic innervation of several salivery and lacrimal glands. The Facial Nerve (VII)
Ask the patient to raise their eyebrows, close their eyes, puff out their cheeks and then show their teeth. Apply resistance if the movement appears to be weak. It is important to remember that eyebrow-sparing facial weakness is a sign of an upper motor neuron lesion, while eyebrow involvement is classically a sign of a facial nerve lesion - particularly Bell’s palsy or Ramsay-Hunt syndrome (herpes zoster).
VIII - HearingThe vestibulocochlear nerve (VIII) supplies special sensory innervation providing feedback on both equilibrium (vestibular system) and hearing (cochlea). The Vestibulocochlear Nerve (VIII) Hearing loss may be conductive, due to external autory canal or middle ear pathology; or sensorineural, due to cochlear or neurologic pathology. The Weber and Rinne tests are used to distinguish between these two types.
If the sound is louder via the auditory meatus, then this is normal or may occur in patients with sensorineural hearing loss. If the sound is louder via the mastoid process, then this suggests conductive hearing loss. IX & X - ThroatThe glossopharyngeal nerve (IX) and vagus nerve (X) serve multiple somatic, visceral and special sensory functions. Together, they provide motor and sensory supply to the pharynx. The Glossopharyngeal Nerve (IX) The Vagus Nerve (X)
XI - Neck & ShouldersThe accessory nerve (XI) supplies motor innervation to laryngeal and pharyngeal muscles; the sternocleidomastoid; and the trapezius. The Accessory Nerve (XI)
XII - TongueThe hypoglossal nerve (XII) provides motor innervation to the intrinsic and extrinsic tongue muscles. The Hypoglossal Nerve (XII) Ask the patient to open their mouth, without protuding the tongue. Look for wasting and fasciculations of the tongue. Next ask the patient to protrude their tongue, looking for tongue deviation, and then ask them to move their tongue to either side. Deviation of the tongue may be a sign of ipsilateral hypoglossal nerve palsy, though may also occur with a contralateral upper motor neuron lesion, motor neurone disease or trauma. Finishing UpThank the patient, turn around and present your findings. Depending on findings, you may offer to perform an upper or lower limb examination looking for signs to confirm your suspicion. Try to localise the patient’s lesion - e.g. to the cerebrum, cerebellum, brainstem, spinal cord, dorsal nerve root, peripheral nerve, neuromuscular junction or muscle. This can be difficult to begin with but with experience, signs will begin to become constellations characteristic of specific lesions. Next Page ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Want more info like this?
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Which of the following is the best way to assess cranial nerve 1?Cranial Nerve I
Occlude one nostril, and place a small bar of soap near the patent nostril and ask the patient to smell the object and report what it is. Making certain the patient's eyes remain closed. Switch nostrils and repeat. Furthermore, ask the patient to compare the strength of the smell in each nostril.
What is the 1st cranial nerve?The olfactory nerve is the first cranial nerve and is instrumental in our sense of smell. The olfactory nerve contains only afferent sensory nerve fibers and, like all cranial nerves, is paired.
Which cranial nerve is tested during the eye assessment?2. Cranial nerve testing. You will already have tested four of the 12 cranial nerves (CNs) during your routine eye exam: II, III, IV and VI.
What does the cranial nerve assessment test for?Cranial Nerve XII
Assess for deviation of the tongue, atrophy, and fasciculations. [3] Atrophy, fasciculations, and deviation in the direction of the lesion are associated with lower motor neuron pathology.
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