anatomy of cranial nerves and its medicolegal importance

1. Cranial nerves-Functions and
Application in Forensic
Medicine
Nafeeya
1st yr PG

2. Overview
Introduction
Classification of Cranial nerves
Course and functions of Cranial nerves
Medico-legal importance
Summary
References

3. Introduction
 12pairs of cranial nerves
 Connects brain to different parts of the body
 Each nerve-Roman numerals[I-XII]
 Intracranial and extracranial
 Development: Ectodermal placode,neural
crest cells, pharyngeal arches

6. Olfactory nerve
 Exit – cribriform plate
 Mediates olfaction [smell]
 Only sensory nerve[SA]
 No precortical relay
Olfactory pathway
 Olfactory receptor cells
 Mitral cells-principle
 Brodmann area 34

7. Lesions:
• Blunt trauma such as coup- contrecoup damage
• Meningitis
• Tumors of the frontal lobe of the brain
• Injury-reduce ablity to smell
 Foster kenedy syndrome:
• Olfactory groove meningioma
• Ipsilateral- anosmia,
• Ipsilateral optic atropy
• Contralateral- papilledema

8. Optic nerve
 Exit - Optic canal
 Nerve of sight
 Transmit all visual
information
 No neurilemma
sheath,so no power to
regenerete,it is a track
not a nerve.
 Special afferent

9. Lesions:
Visual pathway lesions:
Complete blindness
• Bi-temporal and bi-nasal hemianopia
•
• Loss of field of vision
• Multiple sclerosis.
• Orbital apex syndrome:
• Dysfunction of optic nerve – manifested
• vision loss, ptosis, ophthalmoplegia.

10. Oculomotor nerve
 Exits from the Superior orbital fissure
 Functions:
1. Movement of eyeball
2. Constrict pupil
3. Accomodation
4. Convergence
 Innervates-4 EOM ,LPS
 General somatic efferent
 General visceral efferent

11. Lesions:
 Claude’s syndrome
 Uncal herniation
 Microvascular infarction-
DM,HT,CVD
Oculomotor palsy

12. Trochlear nerve
• Exit-Superior orbital fissure
• Function – Abduction of eyeball
• General somatic efferent
• Head injury-Bilateral palsy
• Trochlear nerve pain syndrome
• [trochleitis]-inflamation
• of superior oblique tendon

13. Trigeminal nerve
• Exit-superior orbital fissure, foramen ovalae,
foramen
rotundum
• Functions
1. Largest cn
2. Supplies- mastication
3. Sensory –face,
4. nasal cavity, oral cavity
• General somatic afferent
 Special somatic efferent
 Loss of general sensation of face
 Loss of corneal reflex
 Flaccid paralysis of mastication muscles
 Trigeminal neuralgia

14. Adbucent nerve
• Exit-superior orbital fissure.
• Function –abduction/move
eye towards temporal.
• General somatic efferent
• Lesion-alternating abducent
hemiparesis.
• Paralysis-seen in pateint with
meningitis,subarachnoid
hge,late stage of syphillis,
trauma.

15. Facial nerve
 Stylomastoid foramen
 Facial movements
 Taste
 Salivation
 Lacrimation
 General sensation of external
ear
 Muscles of facial expression
 General somatic afferent,
 Special afferent,
 General visceral efferent,
 Special visceral efferent.

16. Lesions:
• Bells palsy
• Crocodile tear syndrome
• Mobius syndrome
• Guillian barre syndrome
• Ramsay hunt syndrome
• Traumatic facial nerve damage-
blunt/penetrating injury ,# temporal
bone

17. Vestibulococchlear nerve
• Exit-auditory canal
• 2 functional divisions
• *vestibule-maintains equilibrium n
balance.
• *cocchlear –mediates hearing
• Special afferent
• Lesion- disequillibrium , vertigo,
nystagmus,
• Hearing loss
• Meniere’s disease

18. Glossopharygeal nerve
 Exit-jugular foramen
 Functions -
1. Taste
2. Salivation
3. Swallowing
4. Carotid sinus- baroreceptors -regulates blood pressure.
5. Carotid body- chemoreceptors -monitor co2 o2 conc in blood.
 General visceral afferent
 Special afferent
 General visceral efferent
 Special visceral efferent
 Lesion –difficult swallowing ,loss of taste.

19. Vagus nerve
 Exit-jugular foramen
Functions
1. Internal organ function
2. Digestion
3. Swallowing
4. Heart rate
5. Vasomotor activity
6. Reflexes –cough,sneezing,vomiting
 It supplies viscera of neck, throax ,abdomen
 Lesions-paralysis -pharynx, larynx
abnormalities-esophageal motility , gastric acid
secretions , gall bladder emptying

20. Spinal accessory nerve
• Exit-jugular foramen
• Head and shoulder
movements
• sternocleidomastoid
• and trapezius muscle.
• Lesion-difficulty in turning
head and neck , shoulder
drop

21. Hypoglossal nerve
 Exit-Hypoglossal canal
 All tongue movements
 General somatic efferent
 Injuries-sublingual
Surgeries,traumatic
Occipital fracture

22. Recent
 Cranial nerve 13 is also known as the “zero nerve” or “nerve
N”
 First discovered in 1870 in sharks - nerve of pinkus,
 Dysfunction points.
 Cranial nerve 14 was first identified in 1563, it was
mentioned in a textbook as the nerve of Wrisberg .
 Nervus intermedius
 Otalgia

23. Medico-legal Importance

24. MLI Cranial nerves
 Head injury- Olfactory , Oculomotor, facial
 Isolated cn injury –closed head trauma
 Blow –blunt /penetrating – # nasal bones ,ethmoid, maxilla
,malar bone
 Whiplash injury - Cribriform plate # -Anosmia
 Methanol poison-Optic neuropathy
 Neurotoxic snake venom- Oculomotor palsy-ptosis
 Iatrogenic lingual nerve damage-dental procedures

25.  Oral & maxillofacial injuries[RTA]--trigeminal nerve damaged
in angle of mandible-jaw immobile
 Iatrogenic during laryngeal mask placement , tonsillectomy
 Sec304 A
 Cochlear implant helpful- forensic identification
 10-25%-orbital fractures 0.5-3%- blindness
 Café coronary syndrome –fatal chocking of food..
 sec320ipc

26. Cont-
Vagal stimulation Vagal inhibition
•Medical treatment –stimulate vagus
nerve with electrical impulses.
• Benefits –lowers blood
pressure,decreasese heart rate,
reduces body response to stress.
•Vagus nerve stimulation therapy
–epileptic patients.
•Sudden Pressure on neck
•Sudden death
•Hanging
•Strangulation
•Drowning
Implantable vagal stimulator Pathway of vagal inhibition

27. Brain stem death
cranial nerves reflexes
1.Optic nerve[2] Loss of pupillary reflex
2.occulomotor,trochlear,
abducent[3,4,6]
eye motion is lost in reaction
to head
3.Trigeminal ,facial[5,7] Loss of corneal reflex
4.vestibulococchlear[8] Loss of oculo vestibular reflex
5.Glossopharyngeal,vagus[9][
10]
Loss of gag reflex

28. References
1.BD Chaurasia human anatomy head and neck.
2.High yeild neuroanatomy-lippincot williams and wilkins.
3.Colour atlas charles catanese .
4.Clinical neuroanatomy Richard s.snell.
5.Anil agarwal text book of forensic medicine.
6.Narayan reddy essential of forensic medicine.
7.Journal of multidiciplinary healthcare.
8.leg med 2015mar;epub2014 nv 11 J Oral Maxillofac Su
9.journal 2006 Apr;13(3):135-8.epub dec 13
10.Journal of emergency trauma and shock 2018 Jul-
Sep;1
11.Prospective study of hertzernr,feldman,beven,tucker
12.International journal of ophthalmology
13.Journal of critical care medicine