With overuse, the resultant friction may eventually cause painful symptoms, resulting in muscle trauma, bursitis, or inflammation in the area. Intra-articular
Because the iliopsoas or hip flexor crosses directly over the anterior superior labrum of the hip, an intra-articular hip derangement (i.e. labral tears, hip impingement, loose bodies) can lead to an effusion that subsequently produces internal snapping hip symptoms. Causes
The causes of snapping hip syndrome are not fully understood. The onset is often insidious with reports of a "non-painful" sensation or audible snapping, clicking, or popping with certain activities. Individuals often ignore the "snapping" sensation, which may lead to future discomfort with activity. Athletes appear to have an increased risk of snapping hip syndrome due to repetitive and physically demanding movements. Among athletes such as ballet dancers, gymnasts, horse riders, track and field athletes and soccer players, military training, or any vigorous exerciser, repeated hip flexion can lead to injury. In excessive weightlifting or running, the cause is usually attributed to extreme thickening of the tendons in the hip region. Snapping hip syndrome most often occurs in people who are 15 to 40 years old. Extra-articular
Extra-articular snapping hip syndrome is commonly associated with leg length difference (usually the long side is symptomatic), tightness in the iliotibial band (ITB) on the involved side, weakness in hip abductors and external rotators, poor lumbopelvic stability and abnormal foot mechanics (overpronation).
Heroin-induced leukoencephalopathy often involves damage to cerebellar white matter, posterior cerebral white matter, posterior limb of internal capsule, and cerebellar peduncles. The occipital lobe is typically most affected though the frontal, parietal, and temporal lobes have shown involvement as well. Other toxins have been shown to extend damage to other structures of the brain, including the hippocampus, dorsal medulla, and brainstem. Treatment
With such a wide array of causes and unclear understanding of the pathophysiology, there is no known cure or treatment for the disease. In some cases of leukoencephalopathy induced by medications, such as methotrexate and metronidazole, the disease will reduce gradually once the medication is no longer distributed to the patient. Depending on the source of toxicity or pharmacological substance and severity of the white matter damage, many patients can have complete clinical recovery.Coenzyme Q and vitamin supplements, typically vitamin C and vitamin E, and other antioxidant therapies have been suggested to treat heroin-induced leukoencephalopathy patients. However, such treatments have rarely been trialed. See also
Leukoencephalopathy

References
Further reading
Hill MD, Cooper PW, Perry JR (January 2000). "Chasing the dragon – neurological toxicity associated with inhalation of heroin vapour: case report". CMAJ. 162 (2): 236–8. PMC 1232277. PMID 10674060.