Physical changes
Structural and functional MRI imaging show a characteristic pattern of atrophy in the temporal lobes (predominantly on the left), with inferior greater than superior involvement and anterior temporal lobe atrophy greater than posterior. This distinguishes it from Alzheimers disease. Meta-analyses on MRI and FDG-PET studies confirmed these findings by identifying alterations in the inferior temporal poles and amygdalae as the hotspots of disease - brain regions that have been discussed in the context of conceptual knowledge, semantic information processing, and social cognition. Based on these imaging methods, semantic dementia can be regionally dissociated from the other subtypes of frontotemporal lobar degeneration, frontotemporal dementia, and progressive nonfluent aphasia.Selective hypometabolism of glucose has been observed in the anterior temporal lobe, as well as the medial temporal lobe and limbic areas.Damage to white matter tracts connecting the anterior temporal cortex to the inferior longitudinal, arcuate, and uncinate fasciculi, which are regions of the language network, is also seen using diffusion tensor imaging. Imaging also shows the integrity of the axonal connections from the anterior temporal cortex to frontal and posterior associative areas to be altered.Functional abnormalities have also been observed in hippocampal structures, the ventromedial prefrontal cortex, and the cingulate cortex. Memory in dementia: musical objects, musical concepts, and semantic memory
Melodies are a key aspect of musical objects that are thought to form the contents of semantic memory for music. Melodies are defined as familiar tunes that become associated with musical or extra musical meaning.
Cycloplegia is paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation. Because of the paralysis of the ciliary muscle, the curvature of the lens can no longer be adjusted to focus on nearby objects. This results in similar problems as those caused by presbyopia, in which the lens has lost elasticity and can also no longer focus on close-by objects. Cycloplegia with accompanying mydriasis (dilation of pupil) is usually due to topical application of muscarinic antagonists such as atropine and cyclopentolate. Belladonna alkaloids are used for testing the error of refraction and examination of eye. Management
Cycloplegic drugs are generally muscarinic receptor blockers. These include atropine, cyclopentolate, homatropine, scopolamine and tropicamide. They are indicated for use in cycloplegic refraction (to paralyze the ciliary muscle in order to determine the true refractive error of the eye) and the treatment of uveitis. All cycloplegics are also mydriatic (pupil dilating) agents and are used as such during eye examination to better visualize the retina. When cycloplegic drugs are used as a mydriatic to dilate the pupil, the pupil in the normal eye regains its function when the drugs are metabolized or carried away. Some cycloplegic drugs can cause dilation of the pupil for several days. The ones specifically used by ophthalmologists or optometrists wear off in hours, but when the patient leaves the office strong sunglasses are provided for comfort. See also
References
External links
Kels, Barry D.; Grzybowski, Andrzej; Grant-Kels, Jane M. (March 2015). "Human ocular anatomy". Clinics in Dermatology. 33 (2): 140–146. doi:10.1016/j.clindermatol.2014.10.006.