MedicosNotes.com

A site for medical students - Practical,Theory,Osce Notes

Anatomical peculiarity of facialnerve

Facial nerve is a Sensorimotor nerve with the following functions
  • Special visceral efferent (facial muscle)
  • General visceral efferent (submandibular, sublingual and lacrimal glands)
  • Special visceral afferent (taste from anterior two-thirds of tongue)
  • General somatic afferent (sensation from external auditory meatus, mastoid and pinna)
The upper half of the face has a bilateral representation ,whereas the lower half of the face has unilateral representation.
Nuclei of facial nerve are 4 in number
Motor nucleus contains dorsal and ventral group of cells and is situated in ventral pons
Superior Salivatory nucleus control salivation
Nucleus of tractus solitaries carry taste sensation from anterior 2/3 rd of tongue and sensation from external auditory meatus
Lacrimal nucleus. for lacrimation

There is two types of movements voluntary and reflexmovements
Volitional movement
There is supranuclear connection for volitional movement
It is unique for facial nerve
For Volitional movement the fibers start from  lower part of precentral gyrus , corticonuclear fibers descend to pons and cross to opposite facial nucleus. Nucleus  for the superior half of facial muscles receiving ipsilateral and contralateral supranuclear fibers. Nucleus  for the inferior half of facial muscles mainly receive contralateral supranuclear fibers .This explains why the upperhalf is spared in UMN lesion and only lower half is affected.
Variation
Occasionally lower half of face also has ipsilateral supranuclear innervation but it is less than contralateral innervation. This will result in only paresis of lower half in UMN lesion, if ipsilateral supranuclear innervation is also equal to contralateral  innervation both upper half and lower half may escape in UMN lesion.
Rarely upper half will have innervation predominantly from contralateral fibers. Thus in UMN lesion there is extension of weakness to upper half of face also.
For reflex movement 
Fibers from premotor area, extrapyramidal center, basal ganglia, through separate pathway, innervate the Nucleus from both sides but predominantly from Right cortex.
Lesion of this pathway produce Mimic facial palsy.
Nervus intermedius
It is the  Sensory counter part of facial nerve,it carry fibers of Superior Salivatory nucleus, lacrimal nucleus, and Nucleus of tractus solitarius.
It subserves the following
Somatic sensation of mastoid region ,part of pinnae, external auditory canal
Secretomotor fibers to lacrimal gland, salivary glands - sublingual and submandibular and
Visceral sensation – taste sensation from ant. 2/3rd of tongue.

Branches facial nerve

Branches at the Geniculate ganglion 
  • Greater superficial Petrosal nerve -supplies secretomotor fibers to lacrimal gland
Braches of Vertical mastoid segment
  • Nerve to stapedius
  • Chorda tympani -arise 5 mm above the stylomastoid foramen, carry taste sensation from anterior 2/3rd of tongue. It supplies secretomotor fibers to submandibular and sublingual gland
Branches at the level of Stylomastoid foramen
  • Posterior auricular braches-supplies occipitalis and auricular muscles
  • Digastric – Posterior belly of digastric
  • Stylohyoid supplies stylohyoid muscle
Branches in the Parotid region 
Temporofacial  branch
  • Temporal
  • Zygomatic
  • Upper buccal
Cervicofacial branch
  • Lower buccal
  • Mandibular
  • Cervical.
They supply muscles of face, scalp, and platysma.

Course of the facial nerve -the 7th cranial nerve

Key anatomical area you should remember in relation to anatomy of the facial nerve are the following
  • Pons
  • CerebelloPontine angle
  • Internal auditory meatus
  • Middle ear 
  • Stylomastoid foramen
Intrapontine segment 
Pons
Facial nuclei is situated in the pons
Sensory and parasympathetic fibers are carried by nervus intermedius
It curves around the 6th nerve nucleus to form facial collicullus and form the first genu around the 6th Cranial nucleus
Cerebellopontine  Angle
Nerve emerges at the ventrolateral portion of pontomedullary junction with Nervus intermedius and 8th nerve and lies in the cp angle
Meatal segment
Enters the internal auditory meatus with the 8th nerve with the nervus intermiedius in between
Labyrinthine segment
It  dip into the facial canal in the floor of meatal canal, reaches the medial part of tympanic cavity form the 2nd genu - geniculate ganglion – receives the Nervus intermedius.
It curves posteriorly at the genu giving the Greater superfical petrosal nerve at the genu
Then it travels backwards in the horizontal direction (tympanic segment is above the middle ear)
Mastoid segment
It turns back vertically downwards to emerge through stylomastoid foramen, then turns vertically in the vertical (mastoid) segment
It gives nerve to stapedius and chorda tympani nerve in the vertical part
Parotid region
The facial nerve emerge through the Stylomastoid Foramen and enters the parotid region
It emerges at the stylomastoid foramen
Leaves  the parotid gland by dividing to temperofacial and cervicofacial branches
finally divides into five terminal motor branches

What are the Signs and Symptoms of Cushing’s Syndrome

Cushing syndrome produce changes in body fat,skin,bone,muscle,resproductive system,cardiovasular and blood.
Changes in the body fat
  •          Body fat Weight gain
  •        Central obesity
  •          Rounded face
  •          Fat pad on back of neck (“buffalo hump”)
Changes in the Skin
  •  Facial plethora
  •          Thin and brittle skin
  •          Easy bruising,
  •          Broad and purple stretch marks,
  •          Acne
  • ·        Hirsutism
Changes in Bone
  •         Osteopenia
  •          Osteoporosis (vertebral fractures),
  •         Decreased linear growth in children
Changes in muscle
  •          Muscle Weakness
  •          Proximal myopathy (prominent
  • ·        Atrophy of gluteal and upper leg muscles
Changes Metabolism
  • Glucose intolerance/diabetes
  • Dyslipidemia
  • Changes in the Cardiovascular system
  • Hypertension
  • Hypokalemia,
  • Edema
  • Atherosclerosis 
Reproductive system changes
  • Decreased libido,  amenorrhea in women
Blood and immune system changes
  • Increased susceptibility to infections
  • Increased white blood cell count
  • Eosinopenia,
  • Hypercoagulation with increased risk of deep vein thrombosis and pulmonary embolism
Central nervous system changes
  • Irritability
  • Emotional lability
  • Depression,
  • Cognitive defect and paranoid psychosis

How to examine for Collapsing Pulse an OSCE guide

The term collapsing pulse is used to describe a pulse with a rapid upstroke and descent, and is characteristically described in aortic regurgitation.
Other  names of the collapsing pulse
  • Watson's water hammer pulse
  • Cannonball pulse 
  • Pulsus celer.
How to elicit collapsing pulse?
To elicit the collapsing pulse you have to palpate the carotids or the radial pulse.
For the radial pulse:
  • Ask the patient to fully pronate his forearm.
  • Place your right hand on the radial pulse.
  • Grasp the patient's forearm with left hand (with your palm on the flexor aspect of patient's forearm).
  • Raise the hand above the level of the patient's head
  • Repeat the manoeuvre to note the accentuation of the collapse in the elevated position.

How to examine for radiofemoral delay.an OSCE guide

Radiofemoral delay is an important clinical sign that help to detect the coarctation of aorta
How to elicit radiofemoral delay?
To detect the radiofemoral delay you have to palpate the radial and femoral artery simultaneously.Normally the time taken for the pulse wave to reach the radial artery after the cardiac systole is 80 milliseconds and for the femoral artery it is 75milleseconds.If the femoral pulse is delayed compared to radial pulse it is called as radiofemoral delay.
Causes of radiofemoral delay
Coarctation ol aorta
Atherosclerosis of aorta.
Thrombosis or embolism of aorta
 Aortoarteritis.



How to examine for Femoral pulse:an OSCE guide

The femoral pulse is palpated over the ventral thigh between the pubic symphysis and anterior superior iliac spine with the middle and index fingers.
How to examine for femoral pulse?
  • Ask the patient to lie supine,
  • Make the leg partially flexed: abduct and externally rotate the hip,
  • Feel the pulse below the midinguinal point.
Comment on the following
  • Rate, rhythm, character, volume.
  • Character of the vessel wall.
  • Palpability of all vessels.
  • Radio-femoral delay.
Clinical significance
Examination of peripheral pulse is imporatant for detection of radiofemoral delay

This is very important for students preparing for USMLE and MRCP