Phantom limb syndrome (PLS) is a broad classification that refers to a variety of sensory phenomena felt after limb amputation and that may vary in frequency, duration, and intensity. These phenomena include phantom limb sensations, which are the perception that the limb is still present; stump pain, which refers to pain perceived at the location of existing body parts in the region of amputation; and phantom limb pain, which is pain perceived in the absent limb.
Phantom limb pain is uncommon when considering the general population. Consequently, characterization of the epidemiology of phantom limb pain has generally been restricted to the population of patients experiencing amputation. Epidemiologic studies on PLS within amputee populations have consistently reported a high prevalence of phantom limb sensations ranging from 66 to 80% of patients reporting phantom limb sensations 1 year after amputation.
Of the phantom limb sensations, phantom limb pain may occur during the first year after amputation in 50-85% of patients. Chronic pain following amputation is either stump pain or phantom pain or both. Phantom limb pain is frequently described as a paroxysmal burning, crushing, and twisting in the missing part. It peaks within the first month following surgery and may fade slowly as it "telescopes" toward the stump. Patients who experience extremity pain prior to surgery are more likely to develop post-amputation phantom pain and preemptive analgesia with sensory blockade may reduce the incidence of phantom pain. Although the pain may improve, particularly with respect to frequency and duration, it often remains chronic over the course of months or years, either with no improvement or an increase in pain.
Carpal tunnel syndrome (CTS) is one of the most commonly encountered neuropathies in clinical practice and is described as an uncomfortable condition of the wrist and hand that is precipitated by repeated flexion and extension of the wrist causing increased pressure on the median nerve. Although CTS is commonly considered a condition of repetitive movement that may be related to particular occupations, it is also associated with medical conditions including diabetes, rheumatologic and thyroid disorders. CTS symptoms include pain that may radiate up the forearm, numbness, tingling, and reduced sensation in the hand and wrist and the symptoms often worsen at night or after use of the hand. The symptoms usually begin in the dominant hand, although in more than half the cases, the disorder is bilateral.
Clinical examination reveals decreased sensation over the palmar aspect of the thumb through the ring finger. Atrophy of the thenar muscles can occur as a late sign of median nerve neuropathy. Two common physical diagnosis tests, Tinel's sign and Phalen's test, help to confirm the diagnosis. Tinel's sign refers to distal paresthesias produced by percussion of the median nerve either proximal to the flexor retinaculum in the wrist or distally at the base of the palm. Phalen's test is performed by acute flexion of the wrist for 60 s.
Because carpal tunnel syndrome is usually treated surgically, little is known about its natural history. In one clinical study which followed 12 patients with CTS who refused treatment between 4 and 9 years, 7 patients showed improved clinical symptoms and conduction studies over several years, bringing the universally accepted procedure of surgical treatment into some question.
Trigeminal neuralgia (TN), also known as "tic douloureux," is a neuropathic pain condition affecting the facial area. The IASP defines TN as "a sudden, usually unilateral, severe, brief, stabbing, recurrent pain in the distribution of one or more branches of the fifth cranial nerve." Although etiologically it is most frequently associated with vascular compression of the trigeminal nerve, other causes are also observed; between 2 and 4% of cases are associated with multiple sclerosis (MS) and tumors as the underlying cause account for approximately 2% ofcases.
Patients suffering from trigeminal neuralgia describe a paroxysmal pain pattern and these paroxysms, which may only last for a few minutes or seconds, are frequently triggered by non-noxious stimuli or normal activities such as talking, chewing, and swallowing. The pain spreads rapidly at the beginning of the attack, recedes slowly, and is commonly recurrent. It most frequently involves the second and third divisions of the trigeminal nerve (V2 and V3), but can include or be limited to the first division (V1) as well.
The epidemiology of TN has been described in several large population studies, with an annual age- and gender-adjusted incidence of 4.7-8 per 100,000. The incidence is higher in females, with female to male ratios of 1.7-2.2:1, and an incidence that increases with age, peaking at around 70 years.
Glossopharyngeal neuralgia (GPN) refers to a syndrome affecting the ninth cranial nerve that is similar to TN in that it is characterized by paroxysms of excruciating pain lasting seconds to minutes in duration. As with TN, GPN may be idiopathic but is also associated with MS, although probably to a lesser extent than TN. However, in contrast to TN, the pain in GPN is generally localized to the posterior pharynx, tonsillar fossa, and base of the tongue, often with radiation to the external auditory canal or the neck. Its onset is often related to specific trigger factors affecting the throat including swallowing, drinking cold liquids, sneezing, coughing, talking, and clearing the throat.
Glossopharyngeal neuralgia is probably the least well-characterized neuropathic pain condition with respect to pain quality/severity and patient burden. Similarly, its epidemiology is poorly characterized with limited data that suggest the incidence is estimated to be approximately 0.8/100,000 population. The reported peak age of onset is between 70 and 79 years, with similar incidence rates for men and women. The left side was predominantly affected (53%) and bilaterality was noted in 25% of cases.
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