Cranial Nerves Flashcards
Cause of Bilateral Anosmia
due to disease of the olfactory mucus membrane. (Common cold, allergic rhinitis, etc.)
Cause of Unilateral Anosmia
Due to disease affecting olfactory nerves, bulbs, or tract.
(Fractures of the anterior cranial fossa involving the cribriform plate could tear the olfactory nerves, cerebral tumors of the frontal lobe, or meningiomas of the anterior cranial fossa could compress the olfactory bulb or tract)
Visual Defect in Optic Nerve Lesion
Ipsilateral Blindness
Binasal Hemianopia
Optic chiasm lesion
bilateral lateral compression
Bitemporal Hemianopia
Midsaggital transection/ pressure
Right Hemianopia
Optic tract (left) lesion
Right upper quadrantanopia
Optic Radiation (left)
Lower-division
Right lower quadrantonopia
Optic radiation (left) lesion
lower division
Right lower quadrantanopia
Optic Radiation (left) lesion
Upper division
Right hemianopia with macular sparing
Optic radiation (left)
Both divisions
Effects of lesions of the oculomotor nerve
Complete ptosis
Paralysis od upward, downward, and medial movements
Lateral deviation of the eye (External strabismus)
Diplopia
Dilatation of pupil
Loss of accommodation and light reflexes
Lesions of the trochlear nerve
Impaired downward movement with eye adducted
Diplopia on looking down (walking downstairs, reading books etc.)
Effect of lesions of the Ophthalmic nerve (V1)
Loss of pain, touch, and temperature sensation in area supplies
Loss of corneal reflex
Trophic changes in the cornea
Effect of lesions of the Maxillary nerve (V2)
Loss of pain, touch, and temperature sensation in the area supplied
Effect of lesions Mandibular nerve (V3)
Loss of pain, touch, and temperature sensation in the area supplied
Loss of contraction of muscles of mastication
Effects of lesions of the Abducens Nerve
Inability to move the eye outward
Medial deviation of eye (Internal strabismus – squint)
Diplopia
Facial Nerve lesions.
Upper motor neuron lesion → Contralateral lower part of the face paralyzed
Lower motor neuron lesion → Ipsilateral upper & lower parts of the face paralyzed
UMN lesion of the facial nerve.
Ability to wrinkle forehead on both sides
The angle of the mouth will sag & unable to expose teeth fully on the affected side
Contralateral loss of nasolabial fold
Emotional expressions are preserved
The corneal reflex is present
Can close the eye
LMN Lesion of the facial nerve
Inability to wrinkle the forehead on the ipsilateral side
The angle of the mouth will sag & unable to expose teeth fully on the affected side.
Ipsilateral loss of nasolabial fold
Inability to whistle
Emotional expressions are lost
Ipsilateral corneal reflex is absent
The lower eyelid will droop & tears will overflow. Unable to close the eye.
Hyperacusis, loss of taste sensation over the anterior 2/3rd of the tongue can occur (depending on the site of the lesion)
Describe Bell’s Palsy
Dysfunction of the facial nerve as it lies within the facial canal
Usually, unilateral
Produces an LMN type of facial paralysis
Effect of lesion of the vestibular part of the CNVIII
Vertigo (due to disease of the labyrinth such as Meniere disease)
Nystagmus
Effect of lesion of the Cochlear part of the CNVIII
Deafness
Only bilateral temporal lobe lesions cause deafness
Tinnitus
Effect of lesions of the Glossopharyngeal nerve
Unilateral lesions of the Vagus will show little or no gag reflex on the same side
Hoarseness or absence of voice
Lesions involved in the posterior cranial fossa commonly involve the glossopharyngeal, Vagus, hypoglossal nerves as well
Lesions of the Accessory Nerve
Lesions of the spinal part of the accessory nerve will result in paralysis of the sternocleidomastoid & trapezius
Sternocleidomastoid muscle will atrophy causing weakness in turning the head to the opposite side.
The trapezius will atrophy causing the shoulder to droop on the side as well as weakness & difficulty in raising the arm above the horizontal
