Ultrasound assessment of selected peripheral nerves pathologies. Part II: Entrapment neuropathies of the lower limb

Similarly to entrapment neuropathies of upper extremities, the ultrasound constitutes a valuable supplementation of diagnostic examinations performed in patients with suspicions of nerve entrapment syndromes of the lower limb. For many years, it was claimed that such pathologies were rare. This probably resulted from the lack of proper diagnostic tools (including high frequency ultrasound transducers) as well as the lack of sufficient knowledge in this area. In relation to the above, the symptoms of compression neuropathies were frequently interpreted as a manifestation of pathologies of the lumbar part of the spine or a other orthopedic disease (degenerative or overuse one). Consequently, many patients were treated ineffectively for many months and even, years which led to irreparable neurological changes and changes in the motor organ. Apart from a clinical examination, the diagnostics of entrapment neuropathies of lower limb is currently based on imaging tests (ultrasound, magnetic resonance) as well as functional assessments (electromyography). Magnetic resonance imaging is characterized by a relatively low resolution (as compared to ultrasound) which results in limited possibilities of morphological evaluation of the visualized pathology. Electromyography allows for the assessment of nerve function, but does not precisely determine the type and degree of change. This article presents examples of the most common entrapment neuropathies of the lower limb concerning the following nerves: sciatic, femoral, lateral femoral cutaneous, obturator, fibular and its branches, tibial and its branches as well as sural. The pathomorphological basis of the neuropathies as well as corresponding ultrasound images are presented in this paper. Attention has been drawn to echogenicity, degree of vascularization and bundle presentation of the trunk of a pathological peripheral nerve.