Post by Lisa on Mar 2, 2004 19:07:40 GMT -5
The stapedius muscle contracts in response to sound, causing a stiffening of the ossicular chain. The increase in stiffness may be detected by measuring the resistance of the ossicular chain to sound transmission.
Stapedius, along with tensor tympani, is a muscle of the middle ear. It arises from the pyramidal eminence on the posterior wall of the middle ear. It inserts into the neck of the stapes bone.
It acts to pull the stapes posteriorly, so tilting its footplate in relation to the fenestra vestibuli. This has the effect of damping the ossicular chain and hence limits the potential damage caused by loud noise.
Stapedius is innervated by the facial nerve (VII) as it traverses the middle ear. The stapedial reflex is absent in:
otosclerosis
scarring of the middle ear from otitis media cranial nerve VII
The facial nerve is the motor supply to the scalp, facial, and stapedial muscles. It also supplies taste in the anterior two thirds of the tongue via the chorda tympani branch.
When examining cranial nerve VII, look for facial asymmetry; note if there is bilateral facial nerve palsy then symmetry can be maintained.
The causes of facial palsy may be classified in a number of ways:
Unilateral upper motor neurone palsy:
vascular disease
tumour
Unilateral lower motor neurone palsy:
pontine causes:
vascular
tumour
multiple sclerosis
posterior fossa causes:
acoustic neuroma
meningioma
Causes within the petrous temporal bone:
Bell's palsy
Ramsey-Hunt syndrome
otitis media
temporal bone fracture
Glomus tumours
post surgery
Causes distal to the petrous temporal bone:
parotid:
tumour
facial lacerations
Systemic disease:
sarcoidosis
HIV infection
Lyme disease
Unilateral loss of taste can occur, though very rarely, if there are lesions of the middle ear involving the chorda tympani or lingual nerve.
Test muscle power:
ask the patient to wrinkle his forehead - push down on the corrugation on each side - note that this movement is preserved on the side of an upper motor neurone lesion; this is because there is bilateral cortical representation of these muscles
ask the patient to close his eyes and then try to force open each eye
ask the patient to grin
ask the patient to blow out his or her cheeks
if the examiner detects a lower motor neurone lesion then check ears and palate for vesicles of the geniculate ganglion - Ramsay Hunt syndrome
Hyperacusis is an exceptionally acute sense of hearing. It is due to paralysis of the nerve to stapedius from the facial nerve.
This condition may occur in:
withdrawal from benzodiazepines
facial nerve palsy
Ramsay Hunt syndrome
The Ramsay Hunt Syndrome is characterised by sensorineural deafness, vertigo and facial paralysis following Herpes Zoster infection. The patient is usually elderly.
Herpes zoster infects the geniculate ganglion, more rarely the IXth and Xth nerves and, very occasionally, nerves V, VI or XII. Recovery of facial nerve function is less likely than in Bell's palsy. The prognosis may be improved by treatment with acyclovir. The clinical features of Ramsay Hunt Syndrome in temporal sequence of presentation are:
otalgia - pain in the ear and the mastoid region - often with few signs on examination
a vesicular eruption involving the external ear
facial paralysis, deafness and vertigo
ipsilateral loss of taste in the anterior two-thirds of tongue
Stapedius, along with tensor tympani, is a muscle of the middle ear. It arises from the pyramidal eminence on the posterior wall of the middle ear. It inserts into the neck of the stapes bone.
It acts to pull the stapes posteriorly, so tilting its footplate in relation to the fenestra vestibuli. This has the effect of damping the ossicular chain and hence limits the potential damage caused by loud noise.
Stapedius is innervated by the facial nerve (VII) as it traverses the middle ear. The stapedial reflex is absent in:
otosclerosis
scarring of the middle ear from otitis media cranial nerve VII
The facial nerve is the motor supply to the scalp, facial, and stapedial muscles. It also supplies taste in the anterior two thirds of the tongue via the chorda tympani branch.
When examining cranial nerve VII, look for facial asymmetry; note if there is bilateral facial nerve palsy then symmetry can be maintained.
The causes of facial palsy may be classified in a number of ways:
Unilateral upper motor neurone palsy:
vascular disease
tumour
Unilateral lower motor neurone palsy:
pontine causes:
vascular
tumour
multiple sclerosis
posterior fossa causes:
acoustic neuroma
meningioma
Causes within the petrous temporal bone:
Bell's palsy
Ramsey-Hunt syndrome
otitis media
temporal bone fracture
Glomus tumours
post surgery
Causes distal to the petrous temporal bone:
parotid:
tumour
facial lacerations
Systemic disease:
sarcoidosis
HIV infection
Lyme disease
Unilateral loss of taste can occur, though very rarely, if there are lesions of the middle ear involving the chorda tympani or lingual nerve.
Test muscle power:
ask the patient to wrinkle his forehead - push down on the corrugation on each side - note that this movement is preserved on the side of an upper motor neurone lesion; this is because there is bilateral cortical representation of these muscles
ask the patient to close his eyes and then try to force open each eye
ask the patient to grin
ask the patient to blow out his or her cheeks
if the examiner detects a lower motor neurone lesion then check ears and palate for vesicles of the geniculate ganglion - Ramsay Hunt syndrome
Hyperacusis is an exceptionally acute sense of hearing. It is due to paralysis of the nerve to stapedius from the facial nerve.
This condition may occur in:
withdrawal from benzodiazepines
facial nerve palsy
Ramsay Hunt syndrome
The Ramsay Hunt Syndrome is characterised by sensorineural deafness, vertigo and facial paralysis following Herpes Zoster infection. The patient is usually elderly.
Herpes zoster infects the geniculate ganglion, more rarely the IXth and Xth nerves and, very occasionally, nerves V, VI or XII. Recovery of facial nerve function is less likely than in Bell's palsy. The prognosis may be improved by treatment with acyclovir. The clinical features of Ramsay Hunt Syndrome in temporal sequence of presentation are:
otalgia - pain in the ear and the mastoid region - often with few signs on examination
a vesicular eruption involving the external ear
facial paralysis, deafness and vertigo
ipsilateral loss of taste in the anterior two-thirds of tongue
