Delayed crawling or walking are the usual concerns that arise in infants with paralysis of the limb. In these cases, abnormalities of the legs are the main focus of the attention. Diagnosis
Monoplegia is diagnosed by a physician after a physical examination and sometimes after further neurologic examination as well. As monoplegia is fairly rare, after physical examination of a patient complaining of monoplegia, sometimes weakness of an additional limb is also identified and the patient is diagnosed with hemiplegia or paraplegia instead. After neurologic examination of the limb, a diagnosis of a monoplegic limb can be given if the patient receives a Medical Research Council power grade of 0, which is a measurement of the patients limb strength. Needle Electromyography is often used to study all limbs, essentially showing the extent in each limb involvement. Furthermore, magnetic resonance imaging (MRI) is the diagnostic modality of choice for investigating all forms of hemiplegia. It is especially informative to show migrational defects in hemiplegic cerebral palsy associated with seizures.An approach called single-pulse transcranial magnetic stimulation (spTMS) has also been used to help diagnose motor deficits such as monoplegia. This is done by evaluating the functional level of the corticospinal tract through stimulation of the corticospinal lesions in order to obtain neurophysiologic evidence on the integrity of the corticospinal tracts. Single-pulse transcranial magnetic stimulation provides neuropsychological feedback such as motor-evoked potentials (MEPs) and central motor conduction time (CMCT).
While chronic progressive brachial monoplegia is uncommon, syringomyelia and tumors of the cervical cord or brachial plexus may be the cause. The onset of brachial plexus paralysis is usually explosive where pain is the initial feature. Pain localizes to the shoulder but may be more diffuse, or could be limited to the lower arm. Pain is severe and often described as sharp, stabbing, throbbing, or aching. The duration of pain, which is constant, varies from a span of several hours to 3 weeks. As the pain subsides, weakness usually appears. In addition, chronicle progressive weakness of one leg suggests a tumor of the spinal cord of the lumbar plexus. Fever is often the first symptom of lumbar plexus paralysis, followed by pain in one or both legs. The pain has an abrupt onset and may occur in a femoral or sciatic distribution. Weakness may develop concurrently with pain or be delayed for as long as 3 weeks. Furthermore, a monomeric form of spinal muscular atrophy, affecting only one leg or arm, should be considered when progressive weakness is not accompanied by sensory loss. Causes
Some potential causes of monoplegia are listed below.