39. Diseases of the cranial nerves in dogs and cats Flashcards
Cranial Nerves motor sensory and parasympathetic?
Cranial Nerve 1?
CN I (OLFACTORY NERVE)
This nerve is not routinely examined; Unilateral brain lesions do not
cause anosmia (loss of sense of smell); The integration of smell is a bilateral phenomenon
Examination: Objective evaluation of smell function – Behavioural reaction (inaccurate)
Irritating substances will excite CN V sensory nerve endings and will not correlate with olfaction.
Cranial Nerve 2?
CN II (OPTIC NERVE)
Examination:
§ Vision: CN II
§ PLR: CN II → CN III; Tests n. opticus integrity; doesn’t
test vision
§ Menace response (MR): CN II → CN VII; Learned
response at 10-12 weeks; Cerebellar deficit → Ipsilateral
loss of MR
§ Visual placing: CN II → Motoric innervation of the
forelimbs
CN 3?
CN III (OCULOMOTOR NERVE
Pupillary sphincter muscle; Medial, dorsal, ventral recti muscles;
Ventral oblique muscle; Levator palpebrae m. superioris
Examination:
Physiological nystagmus (vestibulo-ocular reflex): Turn the head to
one side and the eye will follow the head’s position in small
fractional movements with fast phase towards the movement.
Dysfunction: Ventrolateral strabismus
CN 4?
CN IV (TROCHLEAR NERVE)
Dorsal oblique muscle
Examination: Physiological nystagmus (vestibulo-ocular reflex)
Turn the head to one side and the eye will follow the head’s position
in small fractional movements with fast phase towards the
movement.
Dysfunction: Dorsolateral strabismus
CN 6?
CN VI (ABDUCENT NERVE)
Lateral rectus muscle; Retractor bulbi muscle
Examination: Physiological nystagmus (vestibulo-ocular reflex)
Turn the head to one side and the eye will follow the head’s position
in small fractional movements with fast phase towards the
movement.
Dysfunction: Medial strabismus
CN 7?
CN VII (FACIAL NERVE)
Motor function: Muscles of facial expression
Sensory function: Sense of taste
Autonomic function: Lacrimal glands; Mandibular glands;
Sublingual salivary glands
Examination:
§ Symmetry of the face § Blinking
§ Corneal reflex § Palpebral reflex
§ Schirmer tear test § Pinching the face
§ Menace response
The facial nerve accompanies the vestibulocochlear nerve (CN VIII)
in the internal acoustic meatus of the petrosal bone → Inflammation
& surgery of the ear can interfere with the function of CN VII
Lesion of CN VII → Facial nerve paralysis
CN VIII?
CN VIII (VESTIBULOCOCHLEAR NERVE)
Function: Hearing; Vestibular function → Adaptation of eye & body
position with respect to the position & movement of the head
Vestibular system: Coordinates position of the eye, neck, trunk &
limbs with the movements of the head. Maintains equilibrium during
active & passive movement when the head is at rest
Function: Receptors detect the position & movement of the head →
Vestibular nuclei in connection with
§ The CN responsible for eye movement (CN III, IV & VI)
§ Ipsilateral extensor muscles of the limb (vestibulospinal
tract)
§ Cerebellum
Vestibular Disease
Clinical signs
§ Vestibular strabismus § Imbalance
§ Vestibular ataxia (asymmetric) § Nystagmus
§ Normal postural reactions § Head tilt
Forms
§ Peripheral (Inner ear)
§ Central (Vestibular nuclei; Cerebellum)
§ Differentiation – Other brainstem signs in central form e.g
postural reaction deficit, nystagmus changes direction with
head position
CN 9?
CN IX (GLOSSOPHARYNGEAL NERVE)
Motor function: Muscles of the pharynx & palate
Sensory function: Tongue & pharyngeal mucosa – Taste
Autonomic function: Salivary glands
Examination: Swallowing & gag reflex (CN IX & X)
Dysfunction: Dysphagia (coughing after drinking)
CN 10?
CN X (VAGUS NERVE)
Motor function: Pharynx; Larynx; Oesophagus
Sensory function: Pharynx; Larynx; Thoracic & abdominal viscera
Autonomic function: Thoracic & abdominal viscera (excl. pelvic
region)
Examination: Swallowing & gag reflex (CN IX & X)
Dysfunction
§ Dysphagia (coughing after drinking)
§ Laryngeal paralysis & voice changes (dysphonia)
§ Megaoesophagus (regurgitation)
CN 11?
CN XI (ACCESSORY NERVE)
Internal branch → Muscles of the larynx & cranial oesophagus
External branch → Mm. trapezius, sternocephalicus et
brachiocephalicus
Dysfunction: Laryngeal paralysis; (Muscle atrophy from ext. branch lesion)
CN 12?
CN XII (HYPOGLOSSAL NERVE)
Function: Motoric innervation of the tongue
Examination
§ Pasty food under the nose – can the animal lick it off?
§ Palpation → Any atrophy felt?
§ Pull the tongue → Can the animal withdraw the tongue?
Dysfunction: Unilateral atrophy of the tongue; Unilateral lingual deviation
Pathological lesions of the cranial nerves?
