Anatomy of brain and brainstem Flashcards
(41 cards)
Midbrain: 3 portions
- Tectum (posterior, roof)
- Tegmentum
- Cerebral peduncles
Tectum
Made of the tectal (quadrigeminal) plate which contains:
- Superior colliculi (visual processing), superior midbrain
- Inferior colliculi (auditory processing), inferior midbrain
Tegmentum
Contains the brainstem nuclei
Auditory pathway
1- Cochlea
2- Cochlear nuclei in the brainstem
3- Superior olivary complex
4- Lateral lemniscus
5- Inferior colliculus in the midbrain
6- Medial geniculate body (MGB) in the thalamus
7- Primary auditory cortex
Sensorineural hearing loss:
- Weber test
- Rinne test
- Weber: lateralizes in the unaffected ear (hears better in the normal ear)
- Rinne: normal/positive (AC>BC)
Conduction hearing loss:
- Weber test
- Rinne test
- Weber: lateralizes in the affected ear (hears better with the abnormal ear)
- Rinne: BC>AC in the affected ear, normal in the unaffected ear (AC>BC)
Main embryonal layer giving rise to the nervous system
Ectoderm
Role of the notochord
- Induces formation of neural plate from the ectoderm
- Gives rise to the vertebral column
Process that turns the neural plate into the neural tube, and when?
Neurulation
3 to 6 weeks gestation
Failure of neurulation leads to
Neural tube defects (NTDs)
At the anterior neuropore: encephalocele or anencephaly
At the posterior neuropore: spina bifida
What is specification
It’s the process of neural tube segmentation into:
- Prosencephalon
- Mesencephalon
- Rhombencephalon
Prosencephalon gives rise to
- Telencephalon: cerebral hemisphere
- Diencephalon: hypothalamus and thalamus
Mesencephalon gives rise to
Midbrain
Rhombencephalon gives rise to
- Brainstem (pons, medulla)
- Cerebellum
Abnormalities during specification leads to
Septo-optic dysplasia
Neural crest cells (from neural tube after it fuses) give rise to
- PNS
- Chromaffin cells of adrenal medulla and melanocytes
What is the notochord made of
Mesodermal cells in contact with the ectoderm
Small, midline tuft of hair over the lower lumbar region
Spina bifida occulta
Child with a tuft of hair over the lumbar region with associated neurologic dysfunction but with no other evidence of NTD
Occult spinal dysraphism
Risk factors for NTD
- Female sex
- Folate deficiency
- Maternal diabetes
- Retinoid exposure
- ASMs: Depakote, Carbamazepine
Chiari I malformation
Displacement of the cerebellum and cerebellar tonsils downward through the foramen magnum
Can be associated with syringomyelia
Chiari II malformation
Displacement of the cerebellar vermis and tonsils in association with a myelomeningocele
Chiari III malformation
Cerebellar herniation into a cervical or occipital encephalocele
What leads to agenesis or dysgenesis of the corpus callosum
Abnormalities in the commissural plate
