Common disorders affecting specific cranial nerves Flashcards
Disorders affecting specific cranial nerves
Idiopathic trigeminal neuropathy
Idiopathic facial neuropathy
Horner’s syndrome
Idiopathic trigeminal neuropathy
Usually affects mandibular branch
Autoimmune neuritis of trigeminal nerves
Underlying causes: carrying heavy things in their mouth, neospora canis, lymphoma
Idiopathic most common
Prediposed breeds: Hungarian vizla, GSD, CKCS
Cats infrequently affected
Clinical signs of idiopathic trigeminal neuropathy
‘Dropped jaw’ with bilateral disease
Mandibular branch of trigeminal nerve most affected - motor innervation to muscles of mastication
- inability to close the mouth
- difficulty prehending food
- muscle atrophy
Can be sensory loss as well
Some show Horner’s syndrome - ophthalmic branch
Diagnosis of idiopathic trigeminal neuropathy
Clinical signs
Exclusion of other underlying causes
MRI of brain and CSF to exclude lymphoma and neospora
Treatment of idiopathic trigeminal neuropathy
Supportive
Hand feeding of soft food or rarely temporary placement of a feeding tube
Muzzle can close mouth partially during recovery
Most animals able tp eat unassisted within 3 weeks and have a full recovery
Idiopathic facial neuropathy
Cause unknown, possibly:
- inflammatory reaction of facial nerves
- potential relationship with herpes virus infection
75% of facial neuropathy in dogs and 25% in cats found to be idiopathic
Cocker spaniels and animals over 5 over represented
Clinical signs of idiopathic facial neuropathy
Unilateral or bilateral
Abnormal facial expression (dropping of ear, lips, eyelids)
Loss of palpebral and corneal reflexes
Dropping food or saliva
If parasympathetic part of facial nerve affected:
- tear production absent/reduced
- neurogenic dry eye
Idiopathic vestibular syndrome
Diagnosis of idiopathic facial neuropathy
Exlcude other causes such as otitis media interna
MRI or CT
Contrast enhancement of faical nerve can be seen on MRI
CSF tap to rule out other underlying disease such as inflammatory/infectious disease
Treatment of idiopathic facial neuropathy
No effective treatment
Eye drops if dry eye
Prognosis is guarded
Full recovery can take 3-6 weeks
Horner’s syndrome pathway
Results from lesions affecting the sympathetic supply to the head
Sympathetic pathway originates in the hypothalamus where the first order neuron is located
Nerve fibres course down the brainstem and cervical spinal cord in tectotegmental spinal tract
Synapse on second order lower motor neuronsin lateral horn of spinal cord segments T1-T3
Second order axons go with roots of brachial plexus (T1-T3)
Fibres continue into thorax to join vasosympathetic trunk
Synapse on third order neuron in cranial cervical ganglion near tympanic bulla
Third order sympathetic fibres pass through middle ear and enter cranial cavity with CN V
Innervate the dilator muscle of the pupil, smooth muscle in the periorbita and eyelids, the third eyelid and the smooth muscles of the head
Localisations of Horner’s syndrome
Brain: intracranial tumours, trauma, inflammation/infection etc.
Cervical and cervicothoracic spinal cord: myelitis, neoplasia, disc disease, fibrocartilaginous embolism
Brachial plexus and ventral roots T1-T3: brachial plexus avulsion, neuritis, truma
Thorax: neoplasia’s, tumours, trauma, iatrogenic, infections etc.
Soft tissues of the neck: tumours, tauma
Tympanic bulla: otitis media/interna, neoplasia, trauma
Idiopathic: most common
Signalment of Horner’s syndrome
More common in dogs than cats
Golden retrievers predisposed for idiopathic Horner’s
Clinical signs of Horner’s syndrome
Miosis
Ptosis
Prolapse of 3rd eyelid
Enolphthalmos
Vasodilation of the vessels of the head
- congestion of conjunctiva/sclera
- pinkness of ear
- heat on palpation
Diagnosis of Horner’s syndrome
Examine all reasonable locations
Physical and neurological examination to rule out brachial plexus avulsion
MRI of brain or spinal cord
Chest x-ray
Treatment of Horner’s syndrome
Dependent on underlying cause
No specific treatment for idiopathic Horner’s
Outcome dependent on underlying cause
Idiopathic Horner’s resolves within 6 months
