The weakness can progress to the opposite limb, although whether this progression is typical or rare is under discussion. Cases of patient improvement and deterioration have both been described, but are atypical. Initially MMA can be confused for slowly progressing case of other neurological diseases such as amyotrophic lateral sclerosis (ALS); initial symptoms can be similar, but their causes are apparently different, and their outcomes markedly so. Diagnostic tools have improved since first described, and a few therapies are being introduced. But sometimes several years of observation are needed before a definitive diagnosis can be made.Use of a cervical collar may afford relief, and some researchers advocate its therapeutic use. There is also a slowly progressive variant of MMA known as OSullivan-McLeod syndrome, which only affects the small muscles of the hand and forearm and has a slowly progressive course. Epidemiology
MMA is described most frequently in Asia, with studies of a few hundred individuals emerging from Japan, China and India; it is much less commonly seen in North America and Europe. The disease (disorder) was first described by Keizo Hirayama in 1959 as "juvenile muscular atrophy of unilateral upper extremity". In 1984 Mandavilli Gourie-Devi (et al.) introduced the term "monomelic amyotrophy". The disease primarily (but not exclusively) affects young (15- to 25-year-old) males. As of 2014 there had been less than 1500 described cases, starting with the patients in Hirayamas 1959 study. The condition is disproportionately high in Asia but no conclusive reason has been found for this.
Middle cerebral artery syndrome is a condition whereby the blood supply from the middle cerebral artery (MCA) is restricted, leading to a reduction of the function of the portions of the brain supplied by that vessel: the lateral aspects of frontal, temporal and parietal lobes, the corona radiata, globus pallidus, caudate and putamen. The MCA is the most common site for the occurrence of ischemic stroke.Depending upon the location and severity of the occlusion, signs and symptoms may vary within the population affected with MCA syndrome. More distal blockages tend to produce milder deficits due to more extensive branching of the artery and less ischemic response. In contrast, the most proximal occlusions result in widespread effects that can lead to significant cerebral edema, increased intracranial pressure, loss of consciousness and could even be fatal. In such occasions, mannitol (osmotic diuretic) or hypertonic saline are given to draw fluid out of the edematous cerebrum to minimise secondary injury. Hypertonic saline is better than mannitol, as mannitol being a diuretic will decrease the mean arterial pressure and since cerebral perfusion is mean arterial pressure minus intracranial pressure, mannitol will also cause a decrease in cerebral perfusion. Contralateral hemiparesis and hemisensory loss of the face, upper and lower extremities is the most common presentation of MCA syndrome. Lower extremity function is more spared than that of the faciobrachial region. The majority of the primary motor and somatosensory cortices are supplied by the MCA and the cortical homunculus can, therefore, be used to localize the defects more precisely.