Auditory Systems

Question 1

Describe the Auditory Pathway.

Answer 1

1. Cochlear Nerve is going to come in and terminate on the Dorsal and Ventral Cochlear Nuclei (ACOUSTIC tubercle is going to be the visual spot on the brainstem where the DORSAL Cochlear Nuclei resides); DORSAL Acoustic STRIAE is going to be visualized as the Stria medullaris Acoustica
2. DORSAL and INTERMEDIATE Acoustic striae will DECUSSATE in the upper medulla and ascend in the CONTRALATERAL Lateral Lemniscus –> Terminates on Inferior Colliculus
   - VENTRAL ACOUSTIC striae will cross the MEDIAL LEMNISCUS and form the Trapezoid Body –> Terminate in the Superior Olivary Nucleus –> Then to INFERIOR COLLICULUS (via the Lateral Lemniscus Pathway)
3. Inferior Colliculus –> Medial Geniculate Body (via the Brachium of the Inferior Colliculus) –> Primary Auditory Cortex (located in the Superior and Transverse Temporal Gyri)
4. Auditory association cortex for the processing and integration of sounds is located in the parieto-occipito-temporal (POT) association cortex and Wernicke’s area.

Question 2

Name the structure that is going to directly link the Auditory Association area to Broca’s area?

Answer 2

Superior longitudinal fasciculus

Question 3

Describe the function of the Superior Olivary Nuclear Complex.

Answer 3

*** Modifying Auditory Information

1. Medial Superior Olivary Nucleus –> Localizing Sound
2. Lateral Superior Olivary Nucleus –> Give rise to most of the OLIVOCOCHLEAR EFFERENTS which are going to mainly INHIBIT the hair cells on the Organ of Corti

Question 4

Describe the various lesions that present with the auditory system:

1. Unilateral Lesion of the Cochlear Nerve
2. Unilateral lesion of the central auditory pathway
3. Lesions of the Primary Auditory Cortex
4. Auditory Agnosia

Answer 4

1. Unilateral Lesion of the Cochlear Nerve - Results in Complete ipsilateral Deafness
2. Unilateral lesion of the central auditory pathway - bilateral diminution of hearing which is more prominent in the contralateral ear. These structures include the lateral lemniscus, inferior colliculus and brachium, and the medial geniculate body.
3. Lesions of the Primary Auditory Cortex - result in a difficulty in localizing sounds and tone discrimination. It does not result in hearing deficits.
4. Auditory Agnosia - Lesions in the auditory association (POT) cortex may result in an auditory agnosia by an inability to comprehend auditory information (spoken and written language as well as other sensory modalities may remain intact)

Question 5

What is the most common type of tumor in the posterior cranial fossa?

How do they present?

Answer 5

Acoustic Neurinomas (Inside the Internal Auditory Meatus)

• 1. Unliateral Deafness*
     
     2. Ataxia
     3. Morning Occipital Headaches
     4. Diplopia
• 5. Unilateral Facial Numbness*
     
     6. Gross papilloedema
     7. Signs of a unilateral cerebellopontine angle tumor
     8. Extensive post-op hemorrhaging

Question 6

Describe Wernicke’s Aphasia.

Answer 6

Damage to Wernicke’s area in the DOMINANT hemisphere

• INABILITY TO COMPREHEND the spoken or written word, but they can SPEAK quite fluently
• Can not really answer a question… They talk all the way around your question and will never get to the point (circumlocution of language)!
• Make up new words (Garbage Truck –> Cabbage Truck)

**** They do not get frusterated! (Broca’s Patients will get FRUSTERATED!!!)

Question 7

Answer 7

1. E
2. C
3. B