Somatosensory Function, Pain, & Headache Flashcards
Describe the function of the somatic nervous system
The somatic nervous system provides awareness of the body, both conscious and autonomic
What aspects does the somatic nervous system cover?
- tactile
- thermal
- position
- pain
Describe tactile, thermal, position, & pain
1. Tactile Pressure/vibration Initial response, often total adaptation 2. Thermal (thermoception) Initial response, partial adaptation 3. Position (proprioception) Sense of limb/body movement without using vision 4. Pain (nociception)
What is pain?
“Unpleasant sensory & emotional sensation associated with actual & potential tissue damage”
- Warns of impending injury
- Motivates seeking help
- Motivates avoidance of future injury
What are the two main pathways of pain?
A & B – “fast pain”
- Large, myelinated
- Pressure/touch, cold, mechanical pain, heat pain
C – “slow pain”
- Small, non-myelinated fibers
- Mechanical/chemical/heat/cold pain
Three Levels of Neurons Involved inSomatic Sensation
First-order: detect the sensation
Second-order: in the spinal cord; transmit message to brain
Third-order:
in the brain
What is a dermatome?
Region of body wall supplied by single pair of dorsal root ganglia
Pain theories: Specificity theory
Pain is a separate modality caused by activity of a specific receptor (nociceptor)
Pain theories: Pattern theory
Pain receptors share pathways and/or nerve endings with other sensory modalities
Example: light touch may not cause pain, but heavy touch of same area may.
Pain theories: Gate control theory
- Neural gate mechanisms in spinal cord can block pain info from going to brain by, for example, involving fibers that sense touch
- Recent research suggests this is a simplistic approach
Pain theories: Neuromatrix theory
- Multifactoral
- Widely distributed neural network with genetic, cognitive and sensory influences
- Helps explain phantom & chronic pain
Describe pain threshold
- Point at which a nociceptive stimulus is perceived as painful
- Uniform from person to person
Describe pain tolerance
- Maximum intensity or duration of pain a person is willing to endure
Variable: - psychological, familial, cultural, environmental
Describe acute pain
Short duration; ceases when cause removed
Serves as a warning
1. Early wave
- Hyperexcitability of neurons
- Secondary wave
- Longer lasting
- Inflammatory reaction to tissue injury
Describe chronic pain
- When pain persists longer than normally expected
- Highly variable
- Often not “usual” pain characteristics
- Peripheral (m/s, organ, vascular)
- Peripheral-central (neuralgias, PLP)
- Central (CNS disease/injury)
Possible negative consequences of Chronic Pain
- Physiological
- Loss of appetite
- Sleep disorders - Psychological
- depression - Familial
- Economic
chronic pain serves no useful purpose
Cutaneous pain
- Arises from skin/subcutaneous tissue
- Sharp, burning, abrupt/slow
- Usually localized
Deep somatic pain
-From deep structures (muscles, tendons, joints, blood vessels)
-Diffuse, radiation
E.g. angina
Visceral pain
- From activation of nociceptors of thoracic, pelvic, abdominal viscera (organs)
- Highly sensitive to distension, ischemia, inflammation (i.e. diseases)
- Relatively insensitive to cutting/burning
- Diffuse, often referred
- Deep/squeezing/sickening
- Accompanied by nausea, vomiting, emotional changes
Referred pain
-Originating in viscera; experienced as pain more near body surface
-Alone or concurrent with localized pain from source
Why?
-Visceral and peripheral neurons converge
-Structures develop nearby as embryo
Describe pain terms
Analgesia: absensce of pain
Hyperalgesia: increased sensitivity to pain
Hypoalgesia: decreased sensitivity to pain
Hyperpathia: unpleasant, prolonged response to pain, explosive
Hyperesthesia: Abnormal increase in sensitivity to sensation
Hypoesthesia: Abnormal decrease in sensitivity to sensations
Paresthesia: Abnormal touch sensation without external stimuli; tingling, pins/needles
Allodynia: Pain produced by stimuli that do not normally cause pain
Causes of neuropathic pain & focal/global
Causes (pathology of nervous system)
Pressure on nerve
Physical/chemical injury to neuron
Infection/ischemia/inflammation of neuron
Focal: trauma/disease of neuron
Global: endocrine disease (DM), neurotoxic meds, chronic alcoholism
Neuropathic pain
Occurring without evidence of provocation
Widespread pain
Sensory deficits
Occurring with light touch (example of allodynia)
Burning/stabbing/etc.
Persistent/intermittent
Neuralgias
Severe, brief, repetitive attacks of lightening-like/throbbing pain along spinal or cranial nerve
Usually precipitated by stimulation of cutaneous region supplied by nerve
So not “neuropathic” as stimulus begins in non-neuronal tissue
Trigeminal neuralgia
Postherpetic neuralgia
Trigeminal Neuralgia
- Most common
- Most severe
- Facial tics/spasms
- Triggers:
- Light touch
- Movement
- Drafts
- Eating
- Possibly d/t trigeminal nerve damage
Postherpetic Neuralgia
-Chronic pain after shingles (herpes zoster)
-Varicella-zoster virus causes damage
-Dormant in dorsal root ganglia
-Variable pain types
Triggers
-Light touch
-Cold wind
-Clothing
Complex Regional Pain Syndrome (CRPS)
- Rare
- Autonomic & vasomotor instability more sensitive that -associated injury warrants
- Begins with one limb, then expands
- Severe pain or hyperalgesia
- Edema, skin blood flow changes
- Abnormal sensorimotor activity
- CRPS-I: no definable injury to nerve
- CRPS-II: allodynia/hyperalgesia after injury
Describe headaches: Primary & Secondary
- Primary
-Migraine/tension-type/cluster/chronic daily - Secondary
-With/following serious disease
-Meningitis, cerebral tumor or aneurysm
-Triggered by disturbed sleep or over-exertion
Accompanied by neurologic symptoms
- Mentation changes, visual or limb disturbances
Describe migraine headaches
-Thought to be inherited
-Without aura (85%)
Pulsatile, throbbing, unilateral
Lasts 1-2 days
-Aggravated by physical activity
-Accompanied by
nausea/vomiting
Light/sound sensitivity
Visual hallucinations (sparks, flashes, etc)
Migraine with Aura
Similar symptoms plus pre-symptoms (aura)
Aura develops over 5-20 minutes, lasts up to one hour
- Characteristics vary but are fully reversible
Visual symptoms
- Flickering lights/spots, loss of vision
Sensory symptoms
- pins/needles, numbess
Speech or neurological disturbances
Retinal Migraine
- Rare
- Recurrent, fully reversible scintillations (light flashes), scotomata (blind spots), blindness in one eye
Chronic migraine
15+ days/month x 3 months
Transformed Migraine
- Similar symptoms to tension-type or sinus headache
- Possibly d/t cranial parasympathetic activation
Childhood periodic syndrome Migraine
- Often related to a serious disease process 3 of the following: -Abdominal pain -N/V -Throbbing h/a -Unilateral location -Aura -Relief with sleep -Positive family hx.
Patho of Migraines
Not well understood
Trigeminal cranial nerve activation is common
Altered hormonal levels
- Estrogen thought to be related
Possible triggers
- Monosodium glutamine, chees, chocolate, etc.
Cluster Headache
Uncommon Possibly hereditary Activation of trigeminal nerve and ANS Possible hypothalamus involvement Men > women 30-70 years old Lasts for weeks/months, then remission
Cluster Headache Manifestations
-Rapid onset pain, lasting 15-180 minutes
-Severe, constant, unilateral
-Orbital most common area
-Can radiate to temple, cheeks, gums
Accompanied by:
-Restlessness/agitation
-Conjunctival redness, lacrimation
-Nasal congestion, rhinorrhea
-Facial sweating
-Miosis (pupil constriction), ptosis, eyelid edema
Tension-Type Headache
-Usually don’t interfere with daily activities
-Dull, aching, diffuse
-Not associated with nausea/vomiting
-Possibly type of migraine
Associated with
-Scalp/neck muscle tension
-Oromandibular dysfunction
-Stress, anxiety, depression
Chronic Daily Headache (CDH)
15+ days/month
No known cause
Often resembles other headache types
Tempomandibular Joint (TMJ) Pain
- Imbalanced joint movement
- Poor bite, bruxism (clenching), inflammation, trauma, degeneration
- Pain: facial, head, neck, ear
Children and Pain
- Respond to nociceptive stimuli as neonates
- Demonstrate pain memory as infants
- Reliable/accurate reporters of pain at young age
Older Adults and Pain
- Common types
- Musculoskeletal (OA, back)
- Rheumatologic (RA)
- Neurologic (DN, postherpetic neuralgia)
- Unrelieved pain can result in
- Gait disturbances, muscle wasting
- Impaired appetite
- Sleep disturbances
- Decreased cognition
- Economic impact
