RSD is the medical abbreviation for Reflex Sympathetic Dystrophy—a disabling disorder resulting in severe pain in one or more limbs, which lasts for several months or longer. RSD is actually an old term used for what is currently known as Chronic Regional Pain Syndrome (CRPS) Type 1, the most common form of the medical condition. RSD is different from the other form of the disease in that there is no significant nerve damage present in RSD patients.
Despite numerous studies, there is still a lot that’s not known or understood about RSD, including what exactly causes it and how it is diagnosed. A clinical diagnosis of RSD is made through observation of signs and symptoms according to criteria such as the Budapest Diagnostic Criteria.
What are the RSD signs and symptoms for RSD diagnosis?
Due to the difficulty in the diagnosis of RSD because of the lack of conclusive tools or tests, most RSD diagnosis are made by observing signs and symptoms. Some of the signs and symptoms that physicians look out for are:
- Deep, aching, cold, burning pain, and/or increased skin sensitivity.
- A noxious event such as a sprain, fracture, or minor surgery which causes the individual pain that is not proportionate to the injury.
- Moderate to severe pain associated with allodynia (pain resulting from a non-painful event such as taking a shower or light touching).
- Heightened sensitivity to painful stimulation (hyperalgesia).
- Swelling in the affected area.
- Abnormal hair or nail growth and skin color changes.
- Sweating in the affected area.
- Limited range of motion, weakness, or other motor disorders such as paralysis or dystonia.
- Skin colour changes.
The Budapest Criteria for RSD diagnosis
A group of pain medicine experts brought together by the International Association for the Study of Pain (IASP) outlined diagnostic criteria for RSD in 1994. This criteria was said to be too sensitive and leading to over-diagnosis. Later in 2003, a closed workshop was held in Budapest, Hungary to re-evaluate these guidelines and modify the criteria for more accuracy in terms of clinical diagnosis of RSD. This new IASP criteria was named the Budapest Criteria because of the location of the workshop where the diagnostic guideline was modified. The Budapest Criteria for diagnosis of RSD is based on observed and patient-reported signs and symptoms and is said to achieve 80% to 90% accuracy when it comes to RSD diagnosis. It is therefore the most recommended way to diagnose an otherwise difficult to identify condition.
The Budapest Criteria for RSD diagnosis is basically a checklist comprised of typical signs and symptoms that a CRPS patient would exhibit. During an examination, the examiner will use the checklist to establish a diagnosis.
How does the Budapest Criteria for RSD diagnosis work?
The Budapest diagnostic criteria is used to differentiate between the signs which the examiner sees or feels on the patient, and symptoms which are reported by the patient. The signs and symptoms are classified under four categories which are:
Refers to symptoms relating to sensitivity. The RSD pain is typically described as continuous burning, shooting, aching, or prickly in nature. Sensory changes are part of the Budapest Criteria for diagnosis of RSD because all patients of the syndrome suffer from hyperalgesia (increased sensitivity to pain) to mechanical stimuli or on joint movement. At least one-third suffer from severe allodynia, which is an increased response to a normally non-painful stimuli. Clinical assessment for sensory changes can be carried out at the bedside using pin prick, cotton wool, joint position, tuning fork, or a hot and cold roller. Quantitative sensory testing which involves mechanical and thermal detection and pain thresholds can also be carried out.
These are usually effects causing or relating to the constriction or dilatation of blood vessels. These effects arise from changes in the autonomic system. In RSD patients, vasomotor disturbances are usually present which such as changes in skin temperature and color.
Sudomotor describes anything that stimulates the sweat glands. The signs related to sudomotor changes include hyper/hypohydrosis and oedema. Oedema is the medical term for fluid retention in the body, which results in swelling of the affected tissue.
Motor refers to movement. A number of factors can lead to altered motor function in patients with RSD. The affected limb can become weak and show coordination deficits. In severe cases of the RSD syndrome, the limb may become useless due to misuse and disuse following bracing and trophic changes. Involuntary movements may also develop such as dystonia and tremor. In advanced stages of RSD, there may be atrophy of the skin, hair, and nails, as well as demineralisation of the bone resulting in osteoporosis.
According to the Budapest Criteria, the following must apply for an RSD diagnosis to be made:
- The patient has continuing pain which is disproportionate to any inciting event.
- The patient has at least one sign in two or more of the categories.
- The patient reports at least one symptom in three or more of the categories.
- No other diagnosis can better explain the signs and symptoms.
Some of the signs and symptoms considered in the Budapest Criteria RSD diagnosis are explained below:
According to the Budapest Criteria, at least one of the following signs must be present in two or more of the following categories for a positive diagnosis of RSD:
- Sensory: The patient exhibits hyperalgesia (to pinprick) which is an enhanced pain response leading to increased sensitivity to pain. Allodynia (to light touch and/or deep physical pressure and/or joint movement) may also be present. This second condition refers to central pain sensitisation from a repetitive stimulation that is not normally painful.
- Vasomotor: In the Budapest Criteria, vasomotor effects to be observed for RSD diagnosis include temperature differences observed between the limb and/or skin colour changes and/or skin colour changes between the limb.
- Sudomotor/Oedema: An examiner may check for oedema and/or sweating changes and/or sweating differences between the limbs.
- Motor/trophic: A relating sign for RSD patients is decreased range of motion and/or motor dysfunction such as weakness, tremor, or muscle spasm; and/or trophic changes (hair and/or nail and/or skin changes).
According to the Budapest Criteria for diagnosis of RSD, a patient must have at least one symptom in three of the following four categories:
- Sensory: Hyperasethesia (abnormal increase in sensitivity) and/or allodynia.
- Vasomotor: Skin colour changes or temperatures and/or skin colour changes between the limbs.
- Sudomotor/oedema: Oedema (swelling) and/or sweating changes and/or sweating differences between the limbs.
- Motor/trophic: Decreased range of motion and/or motor dysfunction (weakness, tremor, muscular spasm (dystonia) and/or trophic changes (changes to the hair and/or nail and/or skin on the limb)).
The Budapest Criteria aids in the diagnosis of RSD by a process of exclusion. To fit the diagnosis after the above-mentioned signs and symptoms are checked for, it is important that no other diagnosis can explain the signs and symptoms. Some differentials that may explain the signs and symptoms observed include:
- Infection (bone, soft tissue, joint or skin)
- Orthopaedic mal-fixation
- Joint instability
- Arthritis or arthrosis
- Bone or soft tissue injury (such as stress fracture, instability or ligament damage)
- Compartment syndrome
- Neural injury (peripheral nerve damage, including compression or entrapment, or central nervous system or spinal lesions)
- Neuropathy (such as from diabetes, alcohol misuse)
- Thoracic outlet syndrome (due to nerve or vascular compression)
- Arterial insufficiency (usually after preceding trauma, artherosclerosis in older people or thrombangitis (Burger’s disease))
- Raynaud’s disease
- Lymphatic or venous obstruction
- Gardner-Diamon syndrome
- Brachial neuritis or plexitis (Parsonage-Turner syndrome or neuralgic amyotrophy)
- Erythromelalgia (may include all limbs)
While the Budapest Criteria for diagnosis of RSD seems simple, a common diagnostic problem is that not all symptoms and signs are always present at the same time. This then calls for supportive investigations such as medical tests that can help with diagnosing the RSD disease.
Medical tests for RSD diagnosis
The first clue pointing to an RSD diagnosis is a lasting pain that is more severe than it should be for the inciting injury. Some medical conditions such as arthritis, Lyme disease, muscle diseases, blood clots in your veins, and small fiber polyneuropathies may exhibit the same symptoms as RSD and must be checked for and ruled out before an RSD diagnosis is given. As mentioned before, there’s no conclusive test for RSD but some tests can help in making the diagnosis, such as:
1. Bone Scans
RSD can exhibit a slight deterioration of bones around the affected area, as well as accumulations of calcium in the bloodstream as a result of this bone loss. A tri-phasic (three phase) bone scan can therefore be used in diagnosing RSD. Before the scan, the patient is given a harmless, intravenous injection of a radioactive tracer substance that typically concentrates in bones. Following that, a gamma camera is used to create images in three phases from the radiation given off by the tracer in the area of the body being examined.
The first phase images are taken immediately and these record the blood flow through the selected area of bone. A few minutes after that, the second phase images are taken and these record blood pooling which may indicate inflammation. Lastly, the third phase images are taken at least two hours later. In that time, most of the tracer substance will have been metabolised by the body. The remaining amount of tracer in the body is analysed and gives indication of the rate of metabolism of tissue within the bones.
The results of a tri-phasic bone scan for a patient with RSD will often show increased blood flow, blood pooling, and delayed metabolism in the affected area. In spite of this, one cannot entirely rely only on a tri-phasic bone scan for the diagnosis of RSD.
X-ray imagery may be helpful in the diagnosis of RSD. From the first stage of the RSD disease, bone loss is identifiable on plain radiographs. The first stage of the disease is characterised by patchy bone loss. As RSD advances, so does the change in bone structure, with diffuse bone loss occurring in the later stages. X-rays may be able to pick up these irregularities or mineral loss from bones, indicating bone loss of at least 30%. These tests can be used to detect changes in the bone as early as two weeks after the onset of RSD so treatment can begin as soon as possible and offer a better chance for managing the disease.
3. Magnetic Resonance Imaging
A Magnetic Resonance Imaging (MRI) scan uses magnets and radio waves to capture images of the body’s internal structure, allowing the physician to see the patient’s bones as well as soft tissues of their body. Though the principle is similar to bone scans, MRI’s use strong magnetism instead of a radioactive material injected into the body, to show a number of tissue irregularities in the affected limb. A magnetic field that temporarily aligns the water molecules in your body is generated during an MRI scan. The radio waves then use these aligned particles to produce faint signals which are recorded as images by the machine. MRIs of patients with RSD often show abnormal signals in skin, soft tissue, joints, bone, and bone marrow during the acute phase of the disease.
4. Thermography test
A thermography test is a sympathetic nervous system test that checks whether the temperature or blood flow is different at the injury site than in other parts of the patient’s body. The reliability of this test with regards to RSD diagnosis is conditional as many other factors can also contribute to a variance in thermographic readings. These include factors such as smoking habits, certain skin lotions that the patient uses, prior history of trauma to the affected area, and recent physical activity. In addition, not all patients who have the RSD disease exhibit an altered thermographic reading, especially when tested in the later stages of the disease.
Normally, if the autonomic nervous system is functioning properly, the patient’s affected extremity will become colder during a thermography test. If the affected extremity warms up instead, this may be an indication of a disruption of the body’s normal thermoregulatory vasoconstrictor function. This may sometimes indicate underlying RSD.
5. Skin temperature readings
One of the points considered in the Budapest Criteria is the skin temperature differences arising from vascular abnormalities associated with the RSD disorder. According to the Budapest criteria, whether the change in temperature is an increase or a decrease, the temperature difference between the affected and unaffected limb must be greater than 1℃ to be considered significant. Infrared thermometry is used to measure skin temperature at the affected and unaffected limbs under resting conditions.
The prognosis of RSD is difficult to determine as the condition may vary from one individual to another. Understanding an RSD diagnosis is important for the patient so they can find ways to manage their pain, as well as the signs and symptoms.