Cutaneous innervation is the supply of sensation to the skin through a network of nerves. These nerves make up part of the peripheral nervous system which feeds information to the brain through the spinal cord. Density of cutaneous innervation can depend in location, as some areas of the body need to be more sensitive than others. The hands and feet, for example, are well supplied with sensation to provide feedback for performing fine motor tasks.
Different spinal nerves supply branches to areas of the body known as dermatomes. Within each dermatome, individual nerves create a network of cutaneous innervation which allows for sensation. The most densely innervated areas of the skin are the exposed mucous membranes like those found around the mouth and genitals. High sensitivity in these locations can protect the body from injury.
Some diseases create a lack of sensation in the skin. Neurological conditions may lead to a loss of cutaneous innervation, which puts a patient at risk of injury and further disease. Sensations felt by the skin can provide important feedback like a warning that a painful ulcer is forming, or that a patient is touching a dangerously hot object. Without these physical sensations, patients may injure themselves and not be aware of it, or could develop complications and not identify them.
A doctor can perform some tests on a patient who appears to have a lack of cutaneous innervation. These can include touching the patient to assess reactions and taking biopsy samples to look for neurons under a microscope. A pathologist can determine if numbers are abnormally low, or if individual neurons show signs of damage that might explain the loss of sensation. Patients with permanent nerve damage may need to take steps to protect themselves like regularly inspecting the skin for injury because they can no longer rely on a warning sign from the nervous system.
Burn victims can also experience a significant loss of cutaneous innervation. These types of injuries can penetrate quickly through to the nerves, destroying these connections along with the skin and connective tissue. Doctors may be able to perform grafts to replace damaged skin and protect the patient, but they cannot replace the lost nerves. As a result, loss of sensation occurs in the burned areas, which means patients may not notice injuries, infection, and other problems. Burns in the hands can also degrade fine motor skills, both by limiting range of motion through scarring and preventing sensitivity by destroying the nerves.