Pathway of Pain

4/5/2014
‘PATHWAY OF PAIN’
ORAL BIOLOGY
PRESENTATION

4/5/2014
PRESENTED BY:
DR.TEHRIM NASEER

4/5/2014
‘PAIN’
An unpleasant sensory and emotional
experience which we primarily associate with
tissue damage or describe in terms of such
damage, or both.

4/5/2014
‘NOCICEPTION’
The detection of tissue damage by
specialized transducers connected to A-
delta and C-fibers.

4/5/2014
CHARACTERISTICS OF
PRIMARY
AFFERENT FIBRES
A-DELTA FIBER:
• Myelinated
• Diameter fine 2 - 5 μm
• 12 - 30 m/sec. conduction velocity
• Terminated at I and V layer
• Fast pain, rapid, pricking and well localized
• Neurotransmitter - Glutamate
• 20% pain conduction

4/5/2014
CHARACTERISTICS OF PRIMARY
AFFERENT FIBRES
C-FIBER:
• Non-Myelinated
• Diameter less than 2 films
• -0.5 to 2 m/s conduction velocity
• Terminate in I and n layers
• Slow, diffuse, dull, aching

4/5/2014
CLASSIFICATION OF PAIN NOCICEPTION
• Proportionate to the stimulation of the nociceptor.
• When acute
•Physiologic pain
•Serves a protective function
•Normal pain
• when chronic
•Pathologic pain

4/5/2014
‘CLASSIFICATION OF PAIN’

4/5/2014
NEUROPATHIC PAIN:
• Sustained by aberrant processes in
PNS or CNS
• Disproportionate to the stimulation of
nociceptor
• Serves no protective function
• Pathologic pain

4/5/2014
MIXED PAIN:
• Nociceptive components
• Neuropathic components
• Examples:
• Failed low-back-surgery syndrome
• Complex regional pain syndrome

4/5/2014
IDIOPATHIC PAIN:
• No underlying lesion found yet, despite
investigation
• Pain disproportionate to the degree of
clinically discernible tissue injury

4/5/2014
‘NORMAL CENTRAL PAIN
MECHANISMS’

4/5/2014
Ascending Tracts Descending Tracts
CORTEX
MIDBRAIN
PONS
MEDULLA
SPINAL CORD
THALAMUS

4/5/2014
‘ASCENDING AND DESCENDING PAIN
PATHWAYS’

4/5/2014
‘PAIN INHIBITORY AND PAIN
FACILITATORY MECHANISMS
WITHIN DORSAL HORN’

4/5/2014
DORSAL HORN GATING MECHANISM

4/5/2014
Neuronal circuitry within the dorsal horn.
Primary afferent neuron axons synapse onto
spinothalmic neurons and onto inhibitory and
excitatory neurons.

4/5/2014
CAUSES OF FACIAL PAIN

4/5/2014
CAUSES OF FACIAL
PAIN
Facial pain can be caused by anything, from an infection to nerve damage in the face.
Common causes for facial pain include:
• oral infections
• ulcers (open sores)
• abscess (collection of pus under the surface tissue in the mouth, for example)
• skin abscess (collection of pus under the skin)
• headache
• facial injury
• toothache

4/5/2014
More serious causes for facial pain include:
• herpes zoster (shingles)
• migraine
• sinusitis (sinus infection)
• nerve disorder

4/5/2014
CHRONIC OROFACIAL
PAIN

4/5/2014
TRIGEMINAL
NEURALGIA
• Tic douloureux / fothergill’s neuralgia
• Paroxysms of fleeting ,excruciating u/l facial pain, usually
lasting less than a minute.
• Usually V2/V3 , rarely V1
• MC – adv age, women , rt side
• Stimulation of trigger zone – pain
• Pain – by activities like talking, chewing, brushing teeth,
exposure to cold, by wind on face

4/5/2014
• Trigeminal / gasserian / semilunar ganglion
• Situated just beside pons in a shallow
depression in petrous apex – meckel’s cave
• Sensory root enters the pons course
dorsomedially & terminate within brainstem:
Nucleus of spinal tract of Vth N
Main/Principal sensory nucleus
Mesencephalic nucleus

4/5/2014
• Fibres – pain & temp – enter spinal tract of
trigeminal & descend to various levels
depending on their somatotropic origin, then
synapse in adjacent nucleus of spinal tract.
• The axons of second order neurons cross
midline, aggregate as trigeminothalamic
tract & ascend to VPM
• From VPM , fibres project through thalamic
radiations to sensory cortex in post central
gyrus

4/5/2014
• B/L Weakness of
muscles of
mastication with
inability to close the
mouth ( dangling
jaw ) – motor neuron
ds, neuromuscular
transmission
disorder, myopathy
Clinical examination
motor functions

4/5/2014
Clinical examination
SENSORY FUNCTIONS
• Pain, touch, heat, cold – tested on face &
mucous membranes
• Each of the 3 divisions of Vth.N is tested
individually and compared with the opposite
side.

4/5/2014
Stimulate Direct
corneal
reflex
Consensual
corneal
reflex
Complete
VthN
lesion
Involved eye Absent Absent
Opposite eye Normal Normal
Complete
VIIthN
lesion
Involved eye Absent Normal
Opposite eye Normal Absent

4/5/2014
Second-Order Neuron; Some times is called a
transmission neuron since it transfer the
impulse on to higher center .
The synapse of the primary afferent and
second-order neuron occurs in the dorsal
horn of the spinal cord .

4/5/2014
Afferent (Sensory) Somatic
Nerves
• – Trigeminal Nerve
• – Facial Nerve
• – Glossopharyngeal Nerve
• – Vagus Nerve
• – Cervical Spinal Nerves

4/5/2014
Efferent (Motor) Somatic
Nerves
– Occulomotor, and abducent Nerves
– Trigeminal Nerve
– Facial Nerve
– Glossopharyngeal nerve

4/5/2014
TYPES OF PAIN
• Myofascial Pain
• Myositis
• Myospasm and Dystonia
• Protective Muscle Splinting
• Contracture
• Neoplasia
• Fibromyalgia

4/5/2014
LEISIONS AND
DISORDERS OF
NERVES

4/5/2014
Supranuclear lesions
• Lesions affecting corticobular pathway -
Contralateral trigeminal motor paresis
(deviation of jaw away from the lesion)
• B/L UMN lesions ( pseudobulbar palsy ) –
trigeminal motor paresis , exaggerated jaw
jerk.Mastication markedly impaired.
• Thalamic lesions – anaesthesia of c/l face
• Parietal lesions – depression of c/l corneal
reflex

4/5/2014
NUCLEAR LEISIONS
• Motor , sensory nuclei – primary/met .
tumours
AV malformations
demyelinating ds
infarction/h’age
syringobulbia
that affect pons, medulla and upper cervical
cord.

4/5/2014
Lesions affecting preganglionic
trigeminal nerve roots
• Tumour ( meningioma, schwannoma, metastasis,
nasopharyngeal ca )
• Infection ( granulomatous, infectious ,
carcinomatous meningitis )
• Trauma
• Aneurysm
Char i/p facial pain, parasthesias, numbness,
sensory loss, corneal reflex depressed, trigeminal
motor paresis.

4/5/2014
Lesions affecting peripheral branches
of VthCranial Nerve
• Ophthalmic div : in middle cranial fossa , at
temporal bone apex, lat wall of cavernous
sinus, sup.orbital fissure, distally in face
• Maxillary div : lower lateral wall of cavernous
sinus, at foramen rotundum, in
pterygopalatine fossa, in floor of orbit, at
infraorbital foramen, in face

4/5/2014
Raeder’s paratrigeminal
syndrome
• U/l oculosympathetic paresis – miosis ,
ptosis (without facial anhydrosis)
• Evidence of trigeminal involvement on same
side.
• d/t lesions in middle cranial fossa ( b/w
trigeminal ganglion & int.carotid.a, near
petrous apex)
• Lesions of gasserain ganglion – tumour,
aneurysm, trauma, infection

4/5/2014
Lesions affecting Gasserian ganglion
• Lesions of middle cranial fossa ( tumour, herpes zoster, sarcoidosis,
syphilis, tuberculosis, arachnoiditis, trauma, abscess )
• Pain – severe & paroxysmal
• Hemifacial / selective div of Vth CN
( esp V2,V3 )
 Parasthesias , numbness may also occur
 Sensory loss depends on div involved
 u/l pterygoid & masseter paresis may occur.

4/5/2014
VISCERAL PAIN PATHWAY
Pain - Aδ and fibers
Travel with autonomic afferent
Spinal cord
(Dorsal Horn)
Lat. spinothalmic tract
Thalamus
Somatosensory Cortex

4/5/2014
‘REFERENCES’
• Guyton and Hall textbook of Medical Physiology
• http://science.howstuffworks.com/life/inside-the-mind/human-
brain/pain3.htm
• http://www.docstoc.com/docs/
• http://www.google.fr/imgres
• www.ksums.net
• www.authorstream.com
• http://www.docstoc.com/docs/70291468/Pain-Terminology-and-Pain-

Pathway of Pain

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Pathway of Pain

Similar to Pathway of Pain (20)

Recently uploaded

Recently uploaded (20)

Pathway of Pain