Sensory disturbances. Pain.

The I.M. Sechenov First Moscow State Medical UniversityChair of nervous diseases

Special• vision, hearing, smell, tasteGeneral• superficial (exteroception)• pain• temperature• tactile• deep (proprioception)• vibration• muscle-joint• spatial• pressure• complex types of sensation• location• stereognosis• visceral (inretoception)

Types of sensation

Types of receptorsSomatosensory receptors in the skin: •Free nerve ending (pain, temperature) •Tactile disk of Merkel •Peritrichial nerve endings around a hair follicle (touch)•Tactile corpuscle of Meissner. •Vater−Pacini corpuscle (pressure, vibration) •End bulb of Krause (cold?)•Ruffini corpuscle (warmth?)

Receptors in muscle, tendons, and fascia:•Annulospiral ending of a muscle spindle (stretch)•Golgi tendon organ (tension)•Golgi−Mazzoni corpuscle (pressure)

Cross section of a mixed peripheral nerve

From Baehr, Duus' Topical Diagnosis in Neurology, 2005, Thieme

Classification of sensory nerve fibres

Type of fibre Sensation Diameter

()

Velocity of conduction

(m/s)

А tactile, vibration 5 - 12 30 - 70

А pain (fast, well localized), cold 2 - 5 12 - 30

Сpain

(delayed, poorly localized), heat

0,4 - 1,2 0,5 - 2

Sensory pathways

The cortical representation of different parts of the body

The cortical representation of different parts of the body in the primary somatosensory cortex of the postcentral gyrus (left) and the primary motor cortex of the precentral gyrus (right) in the human being. (After Penfield, W., H. Jasper: Epilepsy and the Functional Anatomy of the Human Brain. Little, Brown, Boston 1954.)

Sensory disturbances

• Hypoesthesia – decrease of sensation

• Hyperesthesia – increase of sensation

• Anaesthesia – loss of sensation

• Dysesthesia – abnormal sensation

• Paresthesia – sensation of tingling, burning, pricking, or numbness of a person's skin

Peripheral(polyneuropathic)

Peripheral(mononeuropathic)

Types of sensory disturbances

Segmental –radicular

Segmental –dissociated

disturbance:

- All types

- superficial

- deep

sensation

Types of sensory disturbances

Spinal conductive

Types of sensory disturbances

disturbance:

- All types

- superficial

- deep

sensation

Medullar(alternating)

Hemispheral(hemitype)

disturbance:

- All types

- superficial

- deep

sensation

Types of sensory disturbances

MonofilamentCylinder with a plastic

and metal tips Tuning-fork

tactile temperature vibration

Devices to assess the sensation

Additional methods for investigation of sensory fibers

• Electroneuromyography (EMG)the amplitude of evoked potential and velocity of conduction for sensory nerves

• Somatosensory evoked potentials Early and late components

• Quantitative sensory testing Heat, cold, vibration and pain thresholds

PainPain

An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage

International association for the study of pain, 1986

• Transientshort duration• Acutewithin a period of injury and healing• Chronicbeyond the normal healing period

PainPain

• Local• Referred • Irradiating

Nociceptive•is caused by stimulation of peripheral nerve fibers that respond only to stimuli approaching or exceeding harmful intensity (nociceptors); described as throbbing, aching, bursting

Neuropathic•is caused by damage or disease affecting any part of the nervous system involved in bodily feelings (the somatosensory system); described as “burning,” “tingling,” “electrical,” “stabbing,” or “pins and needles

Psychogenic•is pain caused, increased, or prolonged by mental, emotional, or behavioral factors

PainPain

Peripheral mechanisms of neuropathic pain

• Spontaneous ectopic activity

• Sensitization of pain receptors

• Pathological interaction of fibers (ephapse)

• Hypersensitivity to catecholamines

Central mechanisms of pain

• Central sensitization

• “Wind up” phenomenon

• Disinhibition

Gate control theory

Types of pain sensation disturbances

• Hypoalgesia – decrease of pain sensation

• Analgesia – loss of pain sensation

• Hyperalgesia – increase of pain sensation

• Hyperpathia - a painful syndrome characterized by an abnormally painful reaction to a stimulus, especially a repetitive stimulus, as well as an increased threshold

• Allodynia - a pain due to a stimulus which does not normally provoke pain

• Anaesthesia dolorosa - is pain felt in an area (usually of the face) which is completely numb to touch

Neuropathic pain

Trigeminalneuralgia

Postherpetic neuralgia

Diabetic polyneuropathy

Radiculopathy(root compression)

Neuropathic pain

Phantom limb painPost stroke pain

Neuropathic pain

Complex regional pain syndrome

Neuropathic pain

• The most common symptoms overall are burning and electrical sensations, described to be like "shooting pain".

• The patient may also experience muscle spasms, local swelling, abnormally increased sweating, changes in skin temperature (usually hot but sometimes cold) and color (bright red or a reddish violet), softening and thinning of bones, joint tenderness or stiffness, and/or restricted or painful movement.

• Type I, formerly known as reflex sympathetic dystrophy does not have demonstrable nerve lesions.

• Type II, formerly known as causalgia, has evidence of obvious nerve damage.

Diagnosis of pain

• Anamnesis

• Physical investigation

• Evaluation of pain intensity (VAS)

• Additional methods of investigation(MRI, EMG)

• Massage

• TENS

• Acupuncture

• Neurostimulation

• Neurosurgery

• Physiotherapy

• Biofeedback

• Psychotherapy

Non-pharmacological treatment of pain

• Local anesthetics

• NSAIDs

• Opiates

• Antidepressants

• Anticonvulsants

Pharmacological treatment of pain