Contact: Encarnación Martínez Álvarez
This repository has been created to share my investigation project about the brain, specifically of the Cortical Deafness and the Auditory Agnosia. At the moment the project is in the first phase: “literature review”.
Project of investigation: Cortical Deafness and the Auditory Agnosia
A SHORT INTRODUCTION OF THE BRAIN
The brain belongs to Central Nervous System (CNS) and it is composed by encephalon and spinal cord. The encephalon has three parts: brain, cerebellum and brainstem. The brain has two hemispheric (left and right) and a cerebral cortex and subcortex. Furthermore each lobe is divided in four external lobes: frontal lobe, parietal lobe, temporal lobe and occipital lobe. The cerebral cortexes of the temporal lobes are associated to comprehensive language and its brain damage cause comprehensive language impairments as aphasia, cortical deafness or auditory agnosia. In the subcortex are basal ganglia and auditory radiatons which go from medial geniculate nucleus (thalamus) to temporal cortex. The subcortex is connecting with the language and its lesion may cause comprehensive language impairment too.
The Cortical Deafness (CD) is pathology of the brain that patients are unresponsive to all types of sounds (verbal and no verbal) and its peripheral auditory is intact. This term was created by Wernicke in 1883 that patient had bilateral damage in the temporal lobes. However, the Auditory Agnosia (AA) is a pathology which symptom is incapacity to recognize auditory stimuli. The AA may classify in three general groups:
• Auditory agnosia to sounds, incapacity to recognize family sounds of the environment but they can understand words.
• Word deafness or Pure Word Deafness, incapacity to understand oral language but they can to recognize family environment sounds.
• Amusia: incapacity to recognize feature of the music (melody, key or rhythm) and it may be congenital (before of birth) or acquired (caused by brain damage).
The CD and the AA are associated with damage in the temporal lobes cortexes, auditory radiatons or basal ganglia. Those lesions are produced by pathologies as CVA or they may be associated to other pathologies as virus (simplex herpes), Mitochondrial disorders (MELAS) or syndrome (Landau- Kleffner), that they are affecting to zone connection with language.
Clinic presentations these patients have periphery auditory intact and theirs spontaneous speech, read and write are more preserved than oral repetition or dictated which are seriously affected. When the lesion is very long and it has damaged other lobes, the patient may show other symptoms which will be joined to language impairment.
WHY SHOULD WE RESEARCH CORTICAL DEAFNESS AND AUDITORY AGNOSIA?
Cortical deafness and auditory agnosia are pathologies that patients have difficulties to understand they are hearing. Although CD was identified at the end of the 19th century, nowadays the CD and the AA both are still being rare and uncommon deficits. Given there are not much research about Cortical deafness and Auditory Agnosia and theirs results are so vary that there are several gaps in different aspects of the pathologies they should be investigated.
These pathologies may be not diagnosis correctly because there are patients that do not have language impairment such as auditory agnosia to sounds. They can understand words but they cannot identify environment sounds (e g. ambulance siren) and this deficit may affect the diary life activities. On the other side prelingual children may be diagnosis as sensorineural hearing loss because they do not have any language in the moment of the assessment. The patients with MELAS may be diagnosed as sensorineural hearing loss but it is possible the cochlea is intact and the problem is in the brain lesion.
Studies about CD or AA conclude that the temporal lobes cortex lesion cause these pathologies, but there is not accord what part or parts of the temporal lobes are implicate for produce these language deficits. Other studies have concluded auditory radiatons, basal ganglia even insula lobe may cause CD or AA. Furthermore, if the pathology has been produced by unilateral or bilateral lesion is another question that it is not still clarity. When the lesion is very long and it affect other lobes (frontal, parietal or occipital), language deficits may be confuse, more vary and dubious causality, so the assessment and diagnosis are very complicate these patients. Language impairments are oral repetition and dictate, but spontaneous speech, writer and read are more preserved. Nevertheless, linguistic problems vary between patients even when they have the lesion in the temporal lobe. The hearing is not affected although several studies show audiometries within and without sensorineural hearing loss. However, the test auditory brainstem responses (ABR) of either ear confirm the integrity of the auditory nerves and pathways up to the inferior colliculi of both sides. That mean the auditory has not problems and the patient can hearing.
The rehabilitation to those pathologies does almost not exist. Some studies suggest lips reading or language signed to they can communicate with other people.
PROPOSAL OF INVESTIGATION
Given researches about cortical deafness and auditory agnosia are limited and theirs results are very vary it is propose an epidemiology study to define those pathologies.
So, the objectives of the study are:
• The brain areas implicate in the cortical deafness and auditory agnosia.
• Etiology of the cortical deafness and auditory agnosia.
• Age in the moment of the lesion and when diagnosis cortical deafness or agnosia auditory.
• Periphery auditory of the patient assessment with audiometry and ABR.
• Gender more affected in the cortical deafness and auditory agnosia.
• Linguistic clinic feature of the cortical deafness and auditory agnosia.
Subsequently to the epidemiology study it is propose the neuronal and cognitive study and establish the rehabilitation to improve the quality of life of the patients. This rehabilitation is open to new technologies that may help patients to communicate with other people of way independent.