Dermatomes Flashcards
What are dermatomes?
Dermatomes are regions of the skin that are innervated by sensory nerves from a single spinal nerve root. These nerve roots emerge from the spinal cord and branch out to supply sensation to specific areas of the body’s surface.
Dermatomes follow a consistent pattern across the body, resembling a map, with each dermatome corresponding to a specific spinal nerve level
Describe the mapping of dermatomes
The dermatomal map is divided into segments, each representing a different spinal nerve level. For example:
Cervical dermatomes cover areas such as the neck, shoulders, arms, and hands.
Thoracic dermatomes innervate the chest and upper abdomen.
Lumbar dermatomes supply sensation to the lower back, buttocks, and legs.
Sacral dermatomes cover the lower abdomen, groin, and genital area.
Within each dermatome, sensory perception, including touch, temperature, and pain, is transmitted to the brain via sensory nerve fibers. When a dermatome is stimulated or affected by injury or pathology, it can result in characteristic sensory symptoms. For example, compression or irritation of a spinal nerve root can lead to pain, numbness, or tingling sensations in the corresponding dermatomal distribution.
Along the thorax and abdomen, the dermatomes are like a stack of discs forming a human, each supplied by a different spinal nerve. Along the arms and the legs, the pattern is different: the dermatomes run longitudinally along the limbs.
Although the general pattern is similar in all people, the precise areas of innervation are as unique to an individual as fingerprints.
Describe the correlation between dermatomes and referred pain
In referred pain, sensory nerve fibers such as that from dermatomes may come together at the same spinal cord level as the general visceral afferent fibers such as that from the heart. When the general visceral sensory fiber is stimulated, the central nervous system does not discern whether the pain is coming from the body wall or the viscera, so it perceives the pain as coming from somewhere on the body wall. So, the pain is “referred to” as the related dermatomes of the same spinal segment
What is proportionality of referred pain?
Proportionality :The size of referred pain is related to the intensity and duration of ongoing/evoked pain. It is often experienced on the same side of the body as the source, but not always.
Explain the clinical applications of dermatomes
Assessment of Nerve Function: Dermatomes are used to assess the function of specific spinal nerves. By testing sensation or reflexes in specific dermatomal areas. This is helpful in the diagnosis of nerve damage or compression.
Diagnosis of Nerve Lesions: A dermatomal pattern of sensory loss or abnormal sensation can help localize the site of nerve injury or compression.
Pain Management:
Dermatomes help in the diagnosis and management of conditions such as radiculopathy (compression of spinal nerve roots), herpes zoster (shingles), and other neuropathic pain syndromes. By identifying the affected dermatome, one can target treatments more effectively.
Anesthesia Administration: Dermatomes are used in regional anesthesia procedures to ensure accurate placement of anesthetic agents. For example, during epidural anesthesia for childbirth or surgery, health practitioners aim to block sensation in specific dermatomes to achieve effective pain relief.
Surgical Planning: Surgeons may use dermatomal maps to plan incisions and approaches for procedures involving the spine or peripheral nerves. Dermatomal supply helps minimize the risk of postoperative sensory deficits.
