Approach to diagnosis in the child with muscle weakness

A five point program for investigation of children with muscle weakness is presented. These points are interpretation of clinical signs and symptoms, genetic study of the patient's family, appropriate biochemical studies, electrodiagnostic studies, and pathological studies. Each of these points are taken up in considerable detail so that the program is presented in logical and detailed fashion. There is an excellent check list for history taking and also for the clinical examination. The significance of the findings of the clinical examination are discussed in commendable detail. The delicate management of obtaining a genetic history and discussing the genetic implications is very important, especially in Duchenne muscular atrophy, myotonic dystrophy, and facioscapulohumeral dystrophy. Biochemical studies may be diagnostic but abnormalities are not always present. The 'serum muscle enzymes' that are often important are creatine phosphokinase (CPK), serum glutamic pyruvic transaminase (SGPT), serum glutamic oxaloacetic transaminase (SGOT), lactate-dehydrogenase (LDH), and aldolase. Electrodiagnostic studies are of two major types: nerve conduction velocity studies, either motor or sensory and performed with surface electrodes, and electromyography carried out with needle electrodes. Slow nerve conduction velocities are important in the diagnosis of peripheral neuropathies. The most useful purpose of electromyography is recognizing myotonia, progressive spinal muscular atrophy, and polymyositis. Pathologic studies of muscle biopsies are of great importance but they demand a satisfactory biopsy and require skillful examination and interpretation. These points are discussed in detail. Ancillary studies are not routine but may be desirable. They include skeletal x-rays, serum electrolytes, especially potassium, erythrocyte sedimentation rate (ESR), cerebrospinal fluid protein, edrophonium (Tensition) test in cases of suspect myasthenia gravis, thyroid function studies, ophthalmologic examination, and a Trichina skin test. (Voris - Chicago)