retrocochlear disorders Flashcards
what are retrocochlear disorders?
conditions that affect the auditory nerve and its connections to the central auditory nervous system (CANS)
what category will be focus on for retrocochlear disorder?
Intracranial neoplasms
what are neoplasms ?
-new growths
-A neoplasm is an abnormal mass of tissue
what is the site of lesion in neoplasms?
A neoplasm is a disorder of the cell cycle
what is the purpose of neoplasms ?
they don’t have one, they just prey on the host and are almost autonomous
what are intracranial neoplasms?
brain tumors
what do we consider items to be brain tumors?
-Benign and malignant tumors
-Mass lesions (such as cysts) of the brain parenchyma (functional tissue of an organ)
-Tumors in the meninges
-Tumors from structures near the brain tissue (pituitary gland and pineal gland tumors) or other sites in the body that affect brain tissue and function
where do intracranial tumors come from ?
they come from neuroglia cells
what are neuroglia cells ?
Neuroglia cells are the non-excitable support cells of the central nervous system as compared to the excitable cells, the neurons
what are the 4 types of neuroglial cells ?
1)Astrocytes
2)Oligodendrocytes
3)Microglia
4)Ependymal cells
what are Astrocytes
-Star-shaped cells
-They support nerve cells and function as electrical insulators
-They provide a barrier at synapses that contain neurotransmitters or hormones such as dopamine
»»>Lack of which is implicated in Parkinson’s disease
-They play a role in the formation of the blood-brain barrier
what are Oligodendrocytes
They are active in the formation of myelin sheaths for the central nerve fibers
what are microglia ?
-These are small glial cells
-They are activated in the presence of inflammation and degenerative processes within the CNS
T-hey also have a phagocytic function
»>They ingest and remove neural residue
-they are clean up cells that eliminate the ugly stuff
what are Ependymal cells
-These are epithelial cells that line the cerebrospinal fluid (CSF) filled brain cavities and spinal cord
»>i.e., the ventricles and the central canal of the spinal cord
-Some ependymal cells are ciliated and facilitate cerebrospinal fluid (CSF) circulation
-They also are involved in the production of CSF
what are the 2 types of tumors?
benign and malignant
what is another name for benign tumors?
neoplasms
what are characteristics of benign tumors
1)Benign tumors are typically slow-growing
2)They often have well-defined borders, so surgical removal can be an effective treatment
They do not metastasize (spread to other areas of the body)
3)The lesion is generally not life-threatening
4)Only rarely will a benign neoplasm kill, if
»»A benign tumor is locally destructive requiring prompt diagnosis and treatment to prevent further auditory, vestibular, and cranial nerve dysfunction
»»The tumor is located in areas of the brain that control vital functions like breathing
-THEY DON’T SPREAD. THEY STAY WHERE THEY SHOWED UP
what are characteristics of Malignant neoplasms/tumors?
-Malignant tumors tend to grow faster and cause invasion and destruction of contiguous structures
-Malignant tumors are life threatening
-They can spread (metastasize) throughout the body leading to death
»»Although it is very rare for a primary brain tumor to spread beyond the brain or spine
what are intrinsic tumors?
-they’re intra-axial
- they originate within the brain tissue (parenchyma)
-Example: Astrocytoma, glioblastoma, and cerebral metastases (typical multiple)
what are extrinsic tumors ?
-they’re extra-axial tumors
-Originate from tissue that is neither neuronal nor glial, including
>All tissue that encase or support the brain substance, including the meninges
»»>Meningiomas are the most common extra-axial tumors in the brain
>Pineal and pituitary glands
>Cranial nerve sheaths
>Cerebral metastases
what are they 4 portions of the temporal bone ?
-petrous
-squamous
-mastoid
-tympanic
what are the 2 types of vascular tumors?
1)Hemangiomas
2)Vascular malformations
what are hemangiomas?
- they show up during the 1st month of life probably resulting from malformation of angioblastic fetal tissue (they’re congential)
-Characterized by initial rapid growth (proliferation phase)
-Followed by a slow period of involution (decrease in size)
-they’re now called vascular malformations
where do vascular malformations appear ?
In the IAC or geniculate ganglion of the VII N located in the fallopian (facial) canal
-they’re not seen in the middle ear cavity or the EAC
vestibular malformations get confused with ?
hemangioma
-they have different cell structure but they still get confused
what are some symptoms of vascular malformations ?
-symptoms show up around their 30s
-cn 7 dysfunction which would lead to a twitch or weakness if the damage is within the geniculate ganglion
-Hemifacial spasm
-Tinnitus
-Conductive hearing loss (commonly with geniculate ganglion site - eroding into the ME cavity)
-Progressive SNHL (commonly reported with IAC site)
-Vertigo (lesion affecting CN VIII)
what do we use to diagnose Vascular Malformations & Hemangioma
-Case history and symptoms
-High resolution CT scan
-MRI with contrast
what are the differential diagnosis to Vascular Malformations & Hemangioma
1)Meningioma
»Irregular margins and may contain flecks of calcium
2)VII N schwannoma
»Less localized than vascular malformations and hemangioma
»A hemangioma produces facial nerve symptoms when it is smaller in size than do CN VII schwannomas
3)Cholesteatoma
»Vascular lesion seen in the ME cavity or invades other nearby structures
how do we treat Vascular Malformations & Hemangioma
surgery
