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Somatic pain disorder is one form of the somatization disorders that is characterized by predominant pain which is usually severe and disabling. The chronic nature of the condition implies that the pain is either persistent or recurring. For the diagnosis of somatic pain disorder to be made, the main symptom i.e. pain should be present for at least 6 months or should be recurring for more than 6 months.
Epidemiology of Somatic Pain Disorder
The estimated lifetime prevalence of somatic pain disorder in a recent community-based German study was 4.1 % in males and 8.2 % in females. Therefore, female gender has been recognized as a possible risk factor for chronic pain disorders and other somatization disorders.
Somatic pain disorder seems to be more common in subjects with family history of anxiety disorders or somatization disorders. This might be related to environmental influences, epigenetic changes due to these environmental influences or genetic predisposition.
Certain genetic mutations are yet to be identified for the predisposition to somatic pain disorder. Certain genetic polymorphisms in the opioid receptors have been linked to chronic pain syndromes, fibromyalgia, and somatic pain disorder. For instance, the overexpression of OPRM1 in fibromyalgia is linked to the severity of the condition.
Childhood experiences, especially traumatic ones, have been also linked to an increased risk of somatic pain disorder. Sexual, physical and emotional abuse in addition to depression has been also shown to increase the risk of somatization disorders in general and somatic pain disorder in particular.
Clinical Features of Somatic Pain Disorder
The main symptom of somatic pain disorder is that of continuous or recurring chronic pain that can be localized to the head, neck or back; joint or abdomen; or to the breast.
The severity of somatic pain disorder can be classified as mild, moderate or severe based on the following clinical features:
- Persistent and serious thoughts about the symptoms
- The presence of high levels of anxiety
- Excessive energy and time devotion to helping with these symptoms
When one of these features is observed in the patient, the classification is known as mild. Patients with moderate somatic pain disorder have two or more of these three features. Finally, patients with severe somatic pain disorder have two or more of these clinical features in addition to the presence of other somatic symptoms that are not pain.
Diagnostic Criteria for Somatic Pain Disorder
The DSM-IV criteria for the diagnosis of somatic pain disorder consist of the following points.
- The pain should be the predominant symptom in the patient and should result in significant disruption of the daily life activities.
- This should be associated with excessive feelings, thoughts and behaviors that are directed against pain.
- The symptoms should be continuous for six months or recurrent for six months or more and cannot be explained by any other medical condition.
Patients who meet the above-mentioned criteria are diagnosed with somatic pain disorder which can be further classified into persistent and mild, moderate or severe. Persistent somatic pain disorder is defined as the marked and severe pain for six months or longer without any intervening periods of recovery in between.
Brain Imaging in Somatic Pain Disorder
Before 2010, the main goal of brain imaging in chronic pain disorders was to answer research only questions and provide new insights into the role of the cortex in the perception of pain. Recently, novel and targeted therapies for chronic pain syndromes including fibromyalgia have emerged based on the results of brain imaging. Nowadays, it is safe to say that cortical perception of pain in patients with somatic pain disorder is impaired.
The first kind of studies in pain perception was concerned with structural connectivity. Magnetic resonance diffusion tensor imaging studies (MR-DTI) make it possible for the radiologist to visualize the connectome of the cortex and understand how certain brain regions relate to each other. MR-DTI showed impaired structural connectivity patterns in the somatic sensory cortex in patients with somatic pain disorder.
Magnetic resonance imaging studies with quantification of gray matter showed that patients with chronic pain syndromes have reduced neocortical gray matter content compared to healthy controls.
Metabolic studies using magnetic resonance spectroscopy showed metabolic derangements mainly in the prefrontal cortex and amygdala in patients with chronic pain.
Additionally, NMDA-glutamate receptors were found to be impaired in patients with somatic pain disorder. Based on these results, research has been going on the utility and effectiveness of D-cycloserine (DCS) in the management of chronic pain.
D-cycloserine given systemically or injected locally in the prefrontal cortex has been found to improve pain perception in animal models. These findings are very promising as they can improve our current treatment options for chronic pain in humans.
Treatment of Somatic Pain Disorder
The treatment of somatic pain disorders has several goals.
Firstly, one should explain the cause and nature of the symptoms and the patient should be assured that these symptoms are not due to any life-threatening condition. For instance, a patient with chronic head pain might be afraid of brain tumors and once this possibility is excluded this issue should be directly addressed with the patient.
The second goal of the treatment plan should be ensuring regular follow-ups that are not symptom driven. If the patient is instructed to return to you only when the symptoms recur, he or she might become convinced that these symptoms are organic in nature and he or she might become dependent on you.
The third goal of your treatment plan should be treating depression or anxiety disorders. Antidepressants, especially selective serotonin reuptake inhibitors, have shown some efficacy in chronic pain syndromes and fibromyalgia. Amitriptyline was also found to be effective in the management of somatic pain disorders.
Group therapy and family therapy is also essential in the management of somatic pain disorders. Patients should understand that their symptoms, despite being inorganic, are real and are understandable to us. They should be assured that we understand how such symptoms can significantly affect their quality of life.
Novel therapeutic options with transcranial direct current stimulation or transcranial magnetic resonance imaging with neuromodulation of the GABArgic system in the prefrontal cortex are promising. These options are still not clinically approved.