An individual is considered amusic if they perform two standard deviations below the mean obtained by musically competent controls.This musical pitch disorder represents a phenotype that serves to identify the associated neuro-genetic factors. Both MRI-based brain structural analyses and electroencephalography (EEG) are common methods employed to uncover brain anomalies associated with amusia (See Neuroanatomy). Additionally, voxel-based morphometry (VBM) is used to detect anatomical differences between the MRIs of amusic brains and musically intact brains, specifically with respect increased and/or decreased amounts of white and grey matter. Classifications
There are two general classifications of amusia: congenital amusia and acquired amusia. Congenital amusia
Congenital amusia, commonly known as tone deafness, refers to a musical disability that cannot be explained by prior brain lesion, hearing loss, cognitive defects, or lack of environmental stimulation, and it affects about 4% of the population. Individuals with congenital amusia seem to lack the musical predispositions with which most people are born. They are unable to recognize or hum familiar tunes even if they have normal audiometry and above-average intellectual and memory skills. Also, they do not show sensitivity to dissonant chords in a melodic context, which, as discussed earlier, is one of the musical predispositions exhibited by infants. The hallmark of congenital amusia is a deficit in fine-grained pitch discrimination, and this deficit is most apparent when congenital amusics are asked to pick out a wrong note in a given melody. If the distance between two successive pitches is small, congenital amusics are not able to detect a pitch change.
Radiographic features
Whilst some symptoms of DSS can be visually identified, many key symptoms of DSS cannot be identified as such. Therefore, radiographic techniques are required to reach a correct diagnosis for DSS. Abnormal features of the axial skeleton
Skull
In the skull, sclerosis is predominantly observed in the cranial vault and skull base. Other symptoms displayed in the skull include dental anomalies such as abnormal dentition, hypodontia and impaired tooth calcification; intracranial calcifications, which is the calcification of the brain parenchyma; narrow optic canal and other cranial foramina. Abnormal features of the appendicular skeleton
Chest
The ribs are sclerotic, truncated, expanded, and featureless. Sclerosis is also present in the sternum, clavicles and scapulae. Pectus carinatum, a chest deformity, is also characteristic of the disease. Long bones
Sclerosis of epiphyses, diaphyses, and metaphyses with increased radiolucency are key characteristics of the disease. In addition, mottled metaphyseal sclerosis and widening are also present in patients. Development of irregular patchy sclerosis along the bone can also be identified, as well as metaphyseal flaring evolve towards Erlenmeyer flask deformity with nonuniform patches of sclerosis, which are especially prevalent in older patients.The metadiaphyses, a portmanteau of the metaphysis and diaphysis, are bulbous and expanded with bowing and relative radiolucency. The expanded regions are also sclerotic and gives the characteristic bone-in-bone appearance. Spine
Platyspondyly is the development of flattened vertebral bodies, which is one of the most notable symptoms as it distinguishes DSS from other similar diseases such as osteosclerosis. It is observed to be most significant in the thoracic region with increased intervertebral spaces.