Neurogenic TOS is the most common form of thoracic outlet syndrome. At the same time, neurogenic TOS is the most challenging form of thoracic outlet syndrome for a physician to diagnose. Symptoms of neurogenic TOS are often non-specific and confusing. A doctor may find a completely normal neurological examination if he doesn’t attempt specific tests for neurogenic TOS. Equally important, patients may not understand the confusing symptoms of neurogenic TOS that might cause them to seek a TOS specialist.
Symptoms of Neurogenic TOS
Compression and damage of the nerves of the brachial plexus cause the symptoms of neurogenic TOS. However, the brachial plexus is quite complex, comprising different nerve fibers, with multiple branches and divisions. Compression of different fibers or branches will cause different symptoms. Additionally, compression may only occur in certain positions of the arms and neck. As a result, patients may fail to understand why they are experiencing pain at certain times, in certain occupations or recreations. Nonetheless, patients suffer considerable pain of different types and causes.
Patients with neurogenic TOS may experience one or more of the following symptoms of the chest, arm, wrist, or hand:
Mechanisms of Pain
In general, doctors divide the mechanisms of pain into two broad categories: nociceptive pain and neuropathic pain.
Firstly, it is helpful to understand the normal pain pathway. Peripheral receptors of various types are located throughout the body. A peripheral receptor might be specialized for pressure, pain, position or temperature. A peripheral nerve typically connects peripheral receptors to the brain. When an appropriate stimulus triggers one of these receptors, the peripheral nerve transmits a signal from the receptor to the spinal cord, where it usually connects to another nerve, and then to the brain.
Second, we can broadly define the two basic mechanisms of pain:
- Nociceptive pain-A normal nerve transmits a pain signal from a normal peripheral receptor to the brain from a site of tissue damage, such as a burn or a cut in the skin.
- Neuropathic pain-A peripheral nerve is damaged somewhere along its course between the peripheral receptor and the brain. The peripheral receptor and overlying tissue are normal. In this case, the brain receives a signal from the abnormal, damaged peripheral nerve, but interprets the signal as coming from the peripheral receptors.
Third, neuropathic pain is a clinical descriptor, but not a specific diagnosis. Bear in mind that pain syndromes are complex. There are pain syndromes that are incompletely understood, and do not fall neatly into these two categories. Complex Regional Pain Syndrome (CRPS) represents one example of such a condition. Neuropathic pain may result from chronic diseases that affect the peripheral nerves, such as diabetes. Additionally, neuropathic pain may be acute or chronic. It can arise from the peripheral nerves, but also from the central nervous system (the brain and spinal cord).
Neurogenic TOS represents one example of neuropathic pain. The peripheral tissues and receptors are normal. However, entrapment and compression of the brachial plexus causes damage to its component nerves. These nerves send abnormal signals to the brain.
All of the different types of peripheral receptors of the arms send peripheral nerve fibers through the brachial plexus. The brachial plexus has a complex branching pattern. Given these facts, one can understand the complexity of symptoms that neurogenic TOS patients experience.