Exam 1 Deck 2 Flashcards
How much CSF is there?
120 mL
CSF is replaced 3x daily
What are some functions of CSF?
Supports and cushions hte brain
Transports nutrients, messengers and waste
Where does CSF come from?
Choroid epithelial cells in the lateral and 4th ventricles
Ependymal cells produce small amount as well
Metabolically active process, using ATP
What is a difference between CSF production and resorption?
Production is an active transport process - requires ATP
Resorption is a pressure-gradient-driven process
(Difference between intracranial pressure and central venous pressure)
What is used as a marker of CSF?
Beta-2 transferrin (or glucose)
What ions are present in greater concentrations in CSF than in blood?
Chloride (Cl), Magnesium (Mg), and Sodium (Na)
Describe the flow of CSF.
Lateral Ventricle - (where it is produced)
Through Foramen of Monro into the 3rd Ventricle
Through Cerebral Aqueduct into the 4th Ventricle
Exits via the Foramina of Luschka (laterally) or Foramen of Magendie (midline)
From here it goes into Subarachnoid space and back via the venous system
Where is CSF resorbed?
Arachnoid granulations in the subarachnoid space
Arachnoid villi function as pressure-dependent one-way valves
What type of molecules (hydrophilic/lipophilic) more readily cross the BBB?
Lipophilic
Where is the BBB not intact?
Hypothalamus - to allow diffusion of hypothalamic hormones
Pineal gland - to allow for pineal secreatins into the general circulation
Choroid plexus - for CSF production purposes, however, they are connected by tight junctions
What is an ependymoma?
Tumor of the ependyma, the lining of the ventricles.
Constitute 5-6% of all glial cell neoplasms, most frequently seen in children younger than 5 years old
What is a hydrocephalus?
Condition where there is an abnormal accumulation of CSF in the ventricles
Puts pressure on the brain
- in children may cause increased head circumference
- in adults may cause headache, nausea, vomiting, papilledema, palsa, coma, etc
What is a communicating hydrocephalus?
The CSF can travel freely through the ventricular system and into the subarachnoid space, but the movement into the venous system (from the subarachnoid space) is partially or totally blocked.
May be caused by tumor, blood, inflammation, infection, or overproduciton of CSF, or congenital absence of arachnoid villi
A problem with CSF resorption (cannot keep up with CSF production)
In what type of hydrocephalus is the issue with resroption not keeping pace with production?
Communicating
What is the treatment for communicating hydrocephalus?
Shunt placement (usually ventriculo-periotneal)
What is a non-communicating hydrocephalus?
Obstruction somewehre in the ventricular system or subarachnoid space, resulting in the CSF being unable to travel freely from start to finish.
Commonly seen in the interventricular foramen, cerebral aqueduct, caudal portions of 4th ventricle, or foramen of the 4th ventricle.
Can be chronic or more acute
Caused by aqueductal stenosis, tumors, cysts, infection, hemorrage or congenital malformations/conditions
What is the treatment for non-communicating hydrocephalus?
Usually surgical to remove the blocakge
What is Dandy Walker Syndrome?
Example of a genetic cause of non-communicating hydrocephalus
There is expansion of 4th ventricle and posterior fossa and obstruction of foramina of Luschka and Magendie.
Mostly females are affected.
What is a colloid cyst?
A cyst containing gelatinous material in the brain. It is almost always found just posterior to the foramen of Monro in the anterior aspect of the third ventricle, originating from the roof of the ventricle. Because of its location, it can cause obstructive hydrocephalus and increased intracranial pressure
This can cause an abrupt loss of consciousness and death.
What is the likely result of obstruction of the exit channels of the fourth ventricle, the foramina of Magendie and Luschka?
enlargement of all parts of the ventricular system
What is NPH?
Normal Pressure Hydrocephaly
It is one of the rare preventable and/or reversible causes of dementia
Patients experience a diagnostic triad consisting of urinary problems (frequency, urgency, or incontinence), impaired gait, and rapid progressive dementia (“wet, wobbly, and wacky”)
Treatment is a shunting procedure to reduce CSF pressure and volume.
Sign is that there is normal opening pressure upon lumbar puncture
What is hydrocephalus ex vacuo?
Not a true hydrocephalus, but an atrophy of the brain resulting in ventricles that are relatively larger than normal since there is loss of white matter.
No increase in ICP, no neurological defecits apart from those attributable to atrophy
May follow a stroke or some other cause of brain atrophy
What is pseudotumor cerebri (idiopathic intracranial hypertension)?
Most commonly seen in obese women of child bearing age and in people w/ chronic renal failure
Related to vitamin A toxicity, endocrinopathies, TCN
Increase in ICP with little evidence on CT or MRI
Treatment includes a program of weight loss, medication, and, if needed, shunting (lumboperitoneal) or optic nerve fenestration.
What is the origin of anterior brain circulation?
Common carotid artery
What is the origin of posterior brain circulation?
subclavian artery to the vertebral artery
Identify the Posterior Cerebral Artery
Identify the Basilar Artery
Identify the vertebral artery
Identify the posterior inferior cerebellar artery (PICA)
Identify the Anterior Inferior Cerebellar Artery (AICA)
Identify the Superior Cerebellar Artery (SCA)
Where does the carotid artery enter the skull?
Cavernous sinus
Name the four segments of the internal carotids
- Cervical
- Intrapetrossal
- Intracavernous
- Cerebral
Approximately how much of the blood supply to the brain is provided by the internal carotids vs vertebral arteries respectively?
Internal Carotids ~75%
Vertebrals ~ 25%
What does the posterior inferior cerebellar artery (PICA) supply?
The dorsolateral medulla
What does the anterior inferior cerebellar artery (AICA) supply?
Lateral and dorsal pons
What does the superior cerebellar artery (SCA) supply?
Lateral and dorsal pons
What is the blood supply to the dorsal and lateral pons?
anterior inferior cerebellar artery (AICA) and the superior cerebellar artery (SCA)
What supplies blood to the midbrain?
basilar artery, including SCA, but also by PCA.
What vessels supply anterior circulation to the brain?
Internal Carotid
Anterior Cerebral
Middle Cerebral
Anterior Communicating (connects)
Posterior communicating artery anastamoses with the posterior circulation
Describe the course of the Middle Cerebral Artery (MCA)
From its origin from the Internal Carotid MCA proceeds laterally to enter and course through the lateral sulcus (Sylvian fissure). MCA supplies most of the lateral surface of the cerebral cortex, including the regions with the main representations of motor, somatosensory, auditory, language and higher cognitive function
Describe the course of the Anterior Cerebral Artery (ACA)
It courses rostromedially, and at the midline it anastomoses with its contralateral counterpart through the anterior communicating artery (AComm). Branches of ACA supply the inferior and medial surfaces of the frontal and parietal lobes, as well as subcortical structures located anteriorly, near the midline (e.g. septum pellucidum and the septal nuclei, anterior hypothalamus, anterior corpus callosum, anterior fornix and the anterior commissure). The territory of ACA includes the margin between the medial and dorsolateral cortical surfaces. The terminal branches of ACA anastomose with branches of PCA and MCA.
Describe the course of the Posterior Cerebral Artery (PCA)
PCA supplies the occipital lobe and the inferior and medial surfaces of the temporal lobe. As noted above, arteries at the edge of the PCA territory anastomose with the terminal arborizations of the ACA and MCA. The overlapping of these territories establishes collateral circulation.
What are the three parts of the venous system in the head?
Superficial Veins
Deep Veins
Venous (Dural) Sinuses
What is the vein of Trolard?
Large vein that communicates between the superior and inferior cerebral veins, establishing an anastomotic channel between the superior sagittal sinus and the middle cerebral vein and, hence, the cavernous sinus
What is the vein of Labbe?
It is the largest channel that crosses the temporal lobe between the lateral (Sylvian) fissure and the transverse sinus, connecting the middle cerebral vein with the transverse sinus
Where is the straight sinus?
Tentorum Cerebelli
Where/What is the Torcula?
Big pool of blood that drains into the transverse sinuses to the jugulars
Where is the superior saggital sinus?
Top of falx cerebri
Where is the inferior saggital sinus?
Base of falx cerebri
What supplies blood to the spinal cord?
2 Posterior Spinal Arteries (PSA)
1 Anterior Spinal Artery (ASA)
What is the Artery of Adamkiewicz?
A particularly large radicular artery
It usually enters on the left side between T9 and T12 and then fuses with the anterior spinal artery, thereby reinforcing the blood supply to the anterior 2/3s of the lumbar and sacral spinal cord, including the lumbo-sacral enlargement
Commonly occluded
What are radicular arteries?
Arterires that feed blood supply to the anterior or posterior spinal arteries
What supplies blood to the motor neurons of the spinal cord?
Anterior Spinal Artery
What supplies blood to sensory neurons in the spinal cord?
Posterior Spinal Arteries
What does the anterior spinal artery supply blood to?
Motor neurons in the spinal cord (anterior) in pink
What does the posterior spinal arteries supply blood to?
Sensory spinal cord neurons (not shaded)
What is the venous supply of the spinal cord?
Anterior and posterior spinal veins
External and internal plexi
Identify the inferior saggital sinus
1
Identify the straight sinus
2
Identify the Internal cerebral vein
3
Identify the vein of Galen
4
Identify the basal vein of Rosenthal
5
Identify the thalamostriate vein
6
Identify the transverse sinus
7
Identify the superior saggital sinus
8
What is a CT?
Computer tomography (CT) scans use multiple Xrays to provide cross-sectional images of the brain. CT shows the brain, skull, other tissues, and abnormalities along a black-to-white scale.
What is the color code for CTs?
White - more radiodense
Black - less radiodense
Some things may be enhanced with contrast dyes
What are some advantages of CT scans?
Fast
Requires less cooperation
Sensitive to hemorrage, mass, CSF and bone abnormalities
Cost effective
Can use life support devices
What are some disadvantages of CT scans?
Use ionizing radiation (can’t be used with pregnant patients)
Contrast media can cause allergy, renal toxicity or other side effects
Lower resolution
What is MRI?
MRI provides detailed, high resolution, images of the brain in axial, sagittal and coronal plains. MRI creates different images to give you better sensitivity and specificity.
What are some advantages of MRI?
Sensitive and specific - higher contrast than CT, and high resolution
Contrast settings can highlight different tissue types
Can tell how old an abnormality is
Can look at blood vessels using flow-weighted
Diffusion weighted imaging (DWI) can detect acute infarction
What is DWI?
Diffusion-Weighted Imaging
MRI scan that is great for identifying acute infarcts
What are some drawbacks of MRIs?
Slow
Need full patient cooperation
Can’t use most life-support devices
How can you tell a CT scan and an MRI apart?
You can tell a scan is a CT scan when you see the clearly defined white bones and gray soft tissues. With MRI, the detail in the soft tissues is much greater.
What are the four major C-shaped structures in the cerebrum?
Lateral Ventricle
Caudate Nucleus
Fornix
Stria Terminalis (always found between the caudate nucleus and the thalamus)
For a structure to be C-shaped, it must have a lateral aspect to it
Identify the caudate nucleus
Where is the choroid plexus?
Black stuff inside the lateral ventricles
Identify the caudate nucleus.
Identify the lateral ventricle
Identify the splenium of the corpus callosum
Where does the fornix originate and end?
Originates at the hippocampal formation (temporal lobe) and ends at the mammilary bodies (hypothalamus)
Identify the fornix
Identify the fornix
Identify the caudate nucleus
Identify the lateral ventricle
Identify the lateral ventricle
Identify the caudate nucleus
Identify the septum pellucidum
Identify the fornix
Identify the splenium of the corpus callosum
Identify the corpus callosum
Identify the lateral ventricle
Identify the caudate nucleus
Identify the fornix
Describe the course of the stria terminalis
always found between the caudate nucleus and the thalamus
Identify the anterior limb of the internal capsule
Identify the genu of the internal capsule
Identify the posterior limb of the internal capsule
What is the function of the internal capsule?
Carries much of the somatosensory information from the body to the cerebral cortex
Also carries the motor information from the cerebral cortex to the body
What information travels through the genu of theinternal capsule?
Somatosensory and motor to the FACE
What information travels through the posterior limb of the internal capsule?
Somatosensory and motor information to the Arms, Trunk and Leg
Identify the caudate nucleus
Identify the putamen of the lenticular nucleus
Identify the globus pallidus of the lenticular nucleus
Identify the thalamus
Identify the corpus callosum
Identify the lateral ventricle
Identify the caudate nucleus
Identify the internal capsule
Identify the putamen
Identify the middle cerebral artery
Identify the septal nuclei
Identify the fornix
Identify the globus pallidus
Identify the anterior commissure
Identify the amygdala
Identify the third ventricle
Identify the putamen
Identify the foramen of Monro
Identify the genu of the internal capsule
Identify the third ventricle
Identify the inferior horn of the lateral ventricle
Identify the thalamus
Identify the posterior limb of the internal capsule
Identify the interpeduncular cistern
Identify the hippocampal formation
Identify the pontine fibers
Identify a cerebral peduncle
Identify the thalamus
Identify the posterior commissure
Identify the cerebral aqueduct
Identify the middle cerebellar peduncle
Identify the fornix
Identify the lateral ventricle
Identify the caudate nucleus
Identify the fourth ventricle
Identify the cerebellum
Identify the Optic Tract
Identify the Oculomotor Nerve
Identify the Substantia Nigra
Identify the cerebral peduncle
Identify the red nucleus
Identify the cerebral aqueduct
Identify teh periaqueductal gray
Identify the superior colliculus
Identify the crossing fibers of the pons
Identify the pontine nuclei
Identify the descending fibers
Identify the superior cerebellar peduncle
Identify the 4th ventricle
Identify the trochlear nerve
Identify the crossing fibers of the pons
Identify the pontine nuclei
Identify the descending fibers
Identify the middle cerebellar peduncle
Identify the abducens nerve
Identify the facial nerve
Identify the 4th ventricle
Identify the descending fibers (pyramids)
Identify the inferior olivary complex
Identify the Raphe nuclei
Identify the 8th nerve
Identify the inferior cerebellar peduncle
Identify the 4th ventricle
Identify the descending fibers (pyramids)
Identify the hypoglossal nerve
Identify the inferior olivary complex
Identify CN IX-XI
Identify the inferior cerebellar peduncle
Identify the 4th ventricle
Identify the descending fibers (pyramids)
Identify the obex
Identify the dorsal columns
What does this image depict?
Pyramidal decussation
Identify the oculomotor nerve
Identify the oculomotor complex
Identify the trochlear nucleus
Identify the trochlear nerve
Identify the abducens nerve
Identify the abducens nucleus
Identify the hypoglossal nerve
Identify the hypoglossal nucleus
Which cell columns contain GSE fibers?
Oculomotor (III)
Trochlear (IV)
Abducens (VI)
Hypoglossal (XII)
These are near the midline
Identify the facial nucleus
Identify the facial nerve
Identify the nucleus ambiguous
Identify the dorsal funiculus
Identify the lateral funiculus
Identify the ventral funiculus
Are dorsal, lateral and ventral funiculi white or gray matter?
white
Identify the dorsal horn
Identify the intermediate horn
Identify the ventral horn
Are the dorsal, intermediate, and ventral horns white or gray matter?
gray
What functions do neurons in the dorsal horn have?
sensory
What functions do neurons in the intermediate horn have?
both sensory and motor (processing)
What function do neurons in the ventral horn have?
motor
In the spinal cord, where are there enlargements and why?
Cervical and lumbar enlargements for additional innervation to arms and legs (added laterally)
Within the ventral horns, how are proximal/distal and flexor/extensor functions distributed?
Recall, ventral horns are motor neurons
More lateral are more distal; more medial are more proximal (trunkal)
More dorsal are flexors; more ventral are extensors
What is Clarke’s Nucleus?
Only found in thoracic spinal cord; related to cerebellum
What is the intermediolateral nucleus?
Nuclei that supply neurons to the sympathetic chain ganglia
How do you test the olfactory nerve?
Close eyes, place an aromatic stimulus under the nostril
Be sure to avoid irritants, such as ammonia
What is Anosmia?
loss of sense of smell that is often accompanied by the loss of sensation of taste
What is parosmia?
a perversion of the sense of smell
What are olfactory hallucinations?
hallucinations of smell that are commonly associated with temporal lobe seizures
What can caues lesions of the olfactory nerve?
Receptor blockage (i.e. temporary from common cold, smoking, viral)
Primary axon damage (fractures of cribiform plate due to head trauma)
Central processes (contusion sor lacerations of bulb, meningoma, aneurysm, tumor)
What is CSF rhinorrhea?
When CSF is found to be leaking through nostrils
CSF leaks through a dural tear brought about by trauma
Identified by measuring glucose or beta-2-transferrin which are markers of CSF
Which Cranial Nerves are purely motor?
CN III, IV, VI, XI, and XII
Which Cranial Nerves are purely sensory?
CN I, II, VIII
Which cranial nerves have both motor and sensory functions?
CN V, VII, IX, X
Generally speaking, are motor cranial nerve nuclei located more medially or laterally?
medially
Generally speaking, are sensory cranial nerve nuclei located more medially or laterally?
Laterally
Which cranial nerve is the only one considered to be part of the CNS?
CN II - Optic Nerve
What is papilledema?
Swelling of the optic nerve - usually implies increased ICP (intracranial pressure)
How can you identify optic atrophy?
Pale optic nerve, not very well demarcated
What is optic neuritis?
Inflammatory response along optic nerve that presents with pain upon eye movement, central visual loss, decreased visual activity, altered color vision, and afferent papillary defect
How do pituitary tumors relate to the optic nerve?
Can compress the optic chiasm and lead to visual problems (specific parts of visual field)
How do you examine the functionality of the optic nerve?
Acuity - eye chart or equivalent
Visual fields - test them
Pupillary reflexes
Fundus examination with opthalmoscope (retina, optic disc, other structures)
Which muscle adducts the eye?
Medial rectus
Which muscle is responsible for eye depression and extorsion?
Inferior rectus
Which muscle is responsible for eye elevation and intorsion?
superior rectus
Which eye is responsible for eye elevation, abduction, and extorsion?
inferior oblique
Which muscle is responsible for eye depression, abduction, and intorsion?
superior oblique (CN IV)
Which muscle is responsible for eye abduction?
Lateral rectus (CN VI)
Which nucleus is responsible for the autonomic functions of the oculomotor nerve?
The Edinger-Westphal nucleus
What types of fibers are in the olfactory nerve?
SVA
What types of fibers are in the optic nerve?
SSA
What types of fibers are in the oculomotor nerve?
GSE, GVE
What types of fibers are in the trochlear nerve?
GSE
What types of fibers are in the trigeminal nerve?
GSA, SVE
What types of fibers are in the abducens nerve?
GSE
What types of fibers are in the facial nerve?
Save Gas Give Saliva
SVE, GSA, GVE, SVA
What types of fibers are in the vestibulocochlear nerve?
SSA
What types of fibers are in the glossopharyngeal nerve?
Save Gas Give Saliva to Godiva
SVE, GSA, GVE, SVA, GVA
What types of fibers are in the vagus nerve?
Save Gas Give Saliva to Godiva
SVE, GSA, GVE, SVA, GVA
What types of fibers are in the spinal accessory nerve?
SVE
What types of fibers are in the hypoglossal nerve?
GSE
What are lesions that can occur to the oculomotor nerve?
3rd Nerve Palsy: Wrinkled forehead, raised eyebrows, ptosis, abducted eye; can e gotten from PCOM aneurysm, pupil involved early on - dilation and light sensitivity
Diabetic 3rd Nerve Palsy: lose nerve but spares pupil/pupilloconstrictor; death from inside out (ischemic lesion)
What is the difference between a 3rd nerve palsy and a diabetic 3rd nerve palsy?
In diabetic, the parasympathetics (pupillary constriction function) of the 3rd nerve are preserved as it is an ischemic event that affects the nerve from the trunk outwards
What is the function of the trochlear nerve?
Innervates the superior oblique - only CN that exits from dorsal brainstem (midbrain)
only CN that is contralateral
What is unique about the trochlear nerve?
Longest intracranial course
Totally contralateral origin
Only nerve to exit from the dorsal brainstem (midbrain)
What would a lesion to the trochlear nerve look like?
Eye is slightly elevated and extorted.
Pt may be tilting head to the normal side so that both eyes can be at same angle to avoid double vision
What are the three branches of the trigeminal nerve?
V1 - opthalmic: leaves via superior orbital fissure
V2 - maxillary: enters through foramen rotundum
V3 - mandibular: enters through foramen ovale
What fibers are in the opthalmic nerve (V1)?
GSA (sensory)
What fibers are in the maxilary nerve (V2)?
GSA (sensory)
What fibers are in the mandibular nerve (V3)?
GSA and SVE (motor and sensory)
What is trigeminal neuralgia?
Common clinical condition where there is a sensory abnormality that presents as repetitive, brief stabbing pains in the absence of numbness
Typically affects those over 40 y/o. Patients ahve trigger zones (around nares, usually)
Symptoms occur mostly during the day
Often affects V2 and V3 and is usually one side
Can be caused by vascular compression
Treatment includes antiepileptics and neurosurgery
How do you test the trigeminal nerve?
Sensation in the 3 branches
Test the corneal reflex
Test mandibular motor strength (deviation to weaker side)
What does the corneal reflex test?
Trigeminal nerve function
What muscle does the abducens innervate?
Lateral rectus muscle
What do lesions in the abducens nerve present as?
Diplopia at a distance
Can be caused by cerebello-pontine angle tumor
Can be involved with increased ICP because it has adhesions to dura
What is an upper motor neuron?
A neuron that originates in the motor cortex and carries motor information down to the brainstem nuclei, where it synapses with cranial nerves, or to lower motor neurons
What is significant about the innervation of the forehead muscles?
bilateral upper motor neuron innervation (facial nerve; CN VII)
Injury to one side means that the forehead is not affected
What is significant about the motor supply of lower facial muscles?
Supplied by the facial nerve (CN VII), by contralateral upper motor neurons only
Therefore if there is an injury, the muscles on the contralateral side will be affected
What do lesions in the facial nerve present as?
Lower motor neuron lesions (to facial nerve itself or brainstem nuclei) result in ipsilateral palsy with upper and lower parts of the face affected (e.g. Bell’s palsy, meningeal process, or a stroke involving CN VII nucleus)
Upper motor neuron lesions (to neurons traveling from motor cortex to synapse on neurons in facial motor nucleus in pons), results in paralysis of mid and lower half of face on contralateral side to the lesion. Upper face is intact (e.g. stroke)
What is Bell’s Palsy?
Neurological deficit to the facial nerve at the lower motor neuron level (causes ipsilateral defects)
What do lesions in the vestibulocochlear nerve cause?
Hearing loss, vertigo, loss of equilibrium, nystagmus and tinnitus
What is nystagmus?
Nystagmus is a term to describe fast, uncontrollable movements of the eyes that may be: Side to side (horizontal nystagmus); Up and down (vertical nystagmus); Rotary (rotary or torsional nystagmus). Depending on the cause, these movements may be in both eyes or in just one eye.
What is tinnitus?
Tinnitus is the medical term for “hearing” noises in your ears when there is no outside source of the sounds.
e.g. ringing
What is sensorineural hearing loss?
Hearing loss in which the cause lies in the vestibulocochlear nerve, inner ear, or central processing centers of the brain
What is conductive hearing loss?
Heraing loss in which the root cause lies in the middle ear, tympanic membrane, or external ear
What are the two types of hearing loss?
Sensorineural and Conductive
What is acoustic neuroma?
Slow-growing tumor that always results in loss of function of CN VIII (and sometimes VII)
What do lesions to the glossopharyngeal nerve present as?
Difficulty swallowing, some taste impairment, impaired gag reflex
How do you test for Glossopharyngeal nerve function?
Gag reflex for the sensory of IX and motor of X
What is Bell’s phenomenon?
When you close your eyes, the eyeballs roll upwards and a bit outwards
What do lesions in the vagus nerve present as?
Impaired gag reflex
Lowering of palatal arch on the side of the lesion
Deviation of uvula to side of the lesion
Hoarseness of voice (paralysis of vocal cord on laryngoscopy)
What do lesions in the spinal accessory nerve present as?
Difficulties with muscles innervated (sternocleidomastoid, trapezius)
How do you test for a spinal accessory nerve deficit?
Asses muscle bulk of sternocleidomastoid and asses ability of patient to tilt face up and turn in opposite direction
Ask patient to shrug shoulder (drop on weak side)
How do you injure the spinal accessory nerve?
Through surgeries that can inadvertently injure the nerve
Trauma - heavy load, suicide attempts
How do you check for hypoglossal nerve damage?
check for tongue protrusion in midline and push against opposite cheek
Tongue deviates to the side of weakness (tongue licks wound)
Slurred speech
How do lesions to the hypoglossal nerve differ if they are in the upper vs lower motor neurons?
LMN - damage to brainstem nucleus or nerve itself from tumors, surgery, etc): tongue deviation to side of the lesion due to unopposed action of opposite muscle. Also, atrophy and fasiculations
UMN- cortical stroke or tumor: tongue deviation away from side of cortical damage and no atrophy or fasiculations
What is pseudobulbar palsy?
Condition caused by bilateral damage to corticobulbar tracts
Symptoms include inability to control facial movements, impaired swallowing (dysphagia), spastic speech, and random crying and laughing
Can be treated with dextromethorphan
What does corticobulbar mean?
between cortex and brainstem
What is dysphagia?
impaired swallowing
What do you see in a LMN hypoglossal nerve lesion?
Tongue deviation towards weak side
UMN lesion results in tongue deviation away from the side of the cortical damage.
What do you see in a UMN hypoglossal nerve lesion?
Tongue deviation away from side of cortical damage
What do you see in a LMN facial nerve lesion?
Issues on same side of the entire face
What do you see in UMN facial nerve lesions?
Lesions affect the lower half on the opposite side
Which neurons does Pseudobulbar palsy affect?
Bilateral neurons of the corticobulbar tracts
What are the three main layers of the embryo?
Ectoderm
Mesoderm
Endoderm
From which embryonic layer does the nervous system originate?
Ectoderm (inner surface)
Microglia and dura mater come from mesoderm
What occurs during the embryologic stage of induction?
A portion of the ectodermal germ layer becomes destined to form the nervous system. Induction culminates in the formation of a thickening in a part of the dorsal ectoderm called the neural plate
What occurs during the embryological stage of neurulation?
Rapid cell proliferation at the margins of the neural plate, altering its configuration so that a midline neural groove forms between neural folds.
Cells lining the groove give rise to the cells of the CNS (Slide 4). The elevated margins of the neural folds grow toward each other, and then fuse in the midline to form a neural tube, which separates from the ectoderm
How does neural tube closure proceed?
Embryo is like a cannoli - closes at middle and then zips up both rostrally and caudally
What cells give rise to the CNS?
Neural tube cells
What cells give rise to the PNS?
Neural crest cells
What is the origin of the ventricular system?
The hole in the neural tube develops into the ventricles of the CNS
What is the timeline of neural tube closure?
Begins at ~22 days, ends at ~26 (anterior) - 28 (posterior) days
What is histogenesis?
Formation of tissues, when cells start proliferating and migrating
Important structures:
- Germinal zone (Proliferative zone)
- Mantle
- Marginal zone
What do the germinal zone cells transition to become?
Some migrate out and differentiate
The rest wil become the ependymal lining and the epithelium of the tela choroidea and choroid plexus
What do the cells in the mantle become?
Gray matter of the CNS
What do cells in the marginal zone become?
White matter of CNS
What is the lamina terminalis?
The cephalic closing of the neural tube - becomes the anterior wall of the 3rd ventricle and the support structure for crossing structures in the brain
What are the components of the 3-vesicle stage of the nervous system?
Prosencephalon
Mesencephalon
Rhombencephalon
What seperates the prosencephalon from the mesencephalon?
mesencephalic flexure
What separates the mesencephalon from the rhombencephalon?
the cervical flexure
What adult structure corresponds to the prosencephalon?
forebrain
What adult structure corresponds to the mesencephalon?
midbrain
What adult structure corresponds to the rhombencephalon?
hindbrain
What occurs in the transition between the 3- and 5-vesicle stages?
Prosencephalon gives rise to the telencephalon (cerebral cortex) and the diencephalon
Mesencephalon remains
Rhombencephalon gives rise to the metencephalon (pons/cerebellum) and the myelencephalon (medulla)
What 5-vesicle stage structure does the cerebral cortex develop from?
Telencephalon
What 5-vesicle stage structure does the midbrain develop from?
Mesencephalon
What 5-vesicle stage structure does the pons/cerebellum develop from?
metencephalon
What 5-vesicle stage structure does the medulla develop from?
myelencephalon
When can we begin to see the optic vesice?
In the 3 vesicle stage (~28 days)
Before caudal closure of nerual tube
What sets the boundary between the metencephalon and the myelencephalon?
The pontine flexure, which is covered by the tela choroidea
What is the sulcus limitans?
A shallow longitudinal groove that extends throughout the length of the neural tube, separating the developing mantle into dorsal and ventral halves and giving the mantle a butterfly shape
What is the Alar plate?
The dorsal half of the mantle of the neural tube that gives rise to the neuronal cell bodies that form nuclei (cell groups or cell columns) that receive and relay input from sensory neurons.
What is the basal plate?
The ventral half of the mantle of the neural tube. The origin of the motor neurons of the spinal cord. Axons of these basal plate derivatives form the ventral roots of the spinal nerves that innervate skeletal muscles
What is the fate of the lumen of the neural tube?
Becomes the central canal in the spinal cord (much smaller)
How does the development of the medulla and its structures unfold?
Yellow - Altar plate (sensory)
Red - basal plate (motor)
Tela choroidea provides roof (Green)
How do structures in the medulla and midbrain differ from in the spinal cord?
(1) in the medulla and pons, the alar plate lies lateral to the basal plate, not dorsal to it
(2) there are migrations of neuroblasts of both plates from the ventricular floor to other locations
(3) “special” sensory and motor structures of the head require new/different cell groups for innervation.
Structures that are rostral to the midbrain (in the diencephalon and elencephalon), as well as the cerebellum, develop from the alar plate.
vs
Are efferent cell columns medial or lateral to the suclus limitans in the midbrain/medulla?
medial (basal plate derivatives = red)
Are afferent cell columns medial or lateral to the sulcus limitans in the medulla/midbrain?
lateral (yellow = derivatives of Alar plate)
What is the Rhombic lip?
Embryonic structure that develops into the cerebellum
Where does the choroid plexus originate from?
tela choroidea and blood vessels
What diencephalonic structure in the adult brain corresponds to the sulcus limitans?
The hypothalamic sulcus
What is the order of the growth of cerebral cortex components from the telencephalon?
Parietal
Frontal
Occipital
Temporal
What proportion of all malformations affect the CNS?
3-Jan
What is the most important factor in determining the pattern of a malformation?
Gestational age of the disruption (not necessarily the details)
What is neurulation?
Neural tube formation (3-4 weeks of gestation)
When does prosencephalic development occur?
5-6 weeks
When does cortical formation occur?
8-24 weeks
What are dysraphic disorders?
Defects in neural tube development - namely failure of fusion of the tube and its mesenchymal coverings by 28th day post conception
What is the most common malformation of the nervous system?
Neural tube defects (dysraphic disorders)
Within this category, anencephaly and myelomeningocele
What condition is caused by a failure of the fusion of the rostral neural tube?
anencephaly/encephalocele
What condition is caused by a failure of the fusion of the caudal neural tube?
Myelomeningocele
When does the anterior end of the nerual tube close?
24 days
When does the posterior end of the neural tube close?
day 26
What is encephalocele?
Restricted failure of the anterior neural tube to close (around day 26)
Always have meningeal +/- cortical tissue extruding through a bony defect
Usually compatible with life
What is myelomeningocele?
Spina bifida aperta
Restricted failure of posterior neural tube closure
Marked by the absence of overlying skin and meninges, and a malformed spinal cord
Can produce impairment in the spinal cord and brain
What are some risk factors for teh development of myelomeningocele?
In utero exposure to alcohol and some medications
Malnutrition (especially folate deficiency)
Diabetes
Obesity
How do you diagnose myelomeningocele or anencephaly?
Alpha-fetoprotein (AFP) is measured in maternal serum
If elevated, repeat and image with ultrasound
What are some ultrasonographic signs of fetal deformities?
What are some symptoms always associated with spinal cord issues of development?
Bowel/bladder incontinence
Sexual dysfunction
What is chiari?
Downward displacement of the cerebellar tonsils
What are the symptoms of Chiari 2 Malformation?
brainstem dysfunction (apnea, cyanotic spells, dysphagia, hydrocephalus)
What is significant about hydrocephalus in the context of Chiari 2 Malformations?
hydrocephalus develops after birth (2-3 weeks and present by 6 weeks)
What are some treatment options for Chiari 2 Malformations?
Surgery upon delivery, protection from contamination and IV antibiotics
Monitor head circumference
Close monitoring
What is prosencephalic development?
The process during which the forebrain (telencephalon and diencephalon) take shape
What structures does the diencephalon develop into?
thalamus
hypothalaus
subthalamic nuclei
What structures do the telencephalon develop into?
cerebral hemispheres
What is a major defect in prosencephalic development?
Failure of cleavage that manifests as the absence of hemispheric separation
This can cause holoprosencephaly to a varying extent.
What type of developmental defect is agenesis of the corpus callosum?
Disorder of the prosencephalic development (midline development)
Can be total or partial
Usually silent (i.e. no symptoms)
What are some issues that affect cortical development?
Disorders of migration
Heterotopia (gray matter in the white matter, often around ventricles): range from asymptomatic to learning disabilities and epilepsy
Lissencephaly (no migration or overmigration)
What is lissencephaly?
Disorder of migration of neurons in cortical development
Type 1 : no migration (smooth brain color)
Type 2 : over migration (erratic, cobblestone brain)
What occurs in type 1 lissencephaly?
No migration of neurons. Gyral simplification
epilepsy, spastic quadriperisis, developmental delays
What occurs in type 2 lissencephaly?
Over-migration of neurons
Excessive number of small cortical gyri
Developmental delay, epilepsy
What is Dandy Walker?
Hydrocephalus
Sporadic or due to isoretinoid use during pregnancy
Consists of:
Hypoplasia or absence of vermis (cerebellum)
Large 4th ventricle (failure of Lushka and Magendie to open)
Elevated lateral sinuses/torcula and large posterior fossa
What is the vermis?
cerebellum
What is syringomyelia (syrinx)?
fluid-filled gliosis (change in glia) lined cavity within the spinal cord
Typically seen with Chiari Malformation Type 1 (CM1)
loss of abdominal reflexes
scoliosis
What is the most common craniofacial malformation identified in newborns?
Cleft Lip/Palate
Which (Cleft Lip +/- Palate, or Cleft palate) is most commonly associated with a syndrome?
Cleft palate (1/2)
Cleft Lip +/- Palate (1/3)
Which craniofacial malformation has ethnic and sex predispositions?
Cleft Lip +/- Palate
more common in asians/native americans, least in blacks
More common in males
How does one identify cleft lip and/or palate?
Transabdominal ultrasound
What is Cerebral palsy?
permanent, non-progressive disorder of movement and posture that causes activity limitation
1/3 are prenatal, 1/3 are perinatal, 1/3 are unknown
What clues lead to a diagnosis of cerebral palsy?
History of motor delay without loss of skills (no walking by 15 months)
Early handedness
Persisting primitive reflexes
Lack of development of protective reflexes
What is lobar holoprosencephaly?
distinct hemispheres with continuity only in the most frontal regions
What is semilobar holoprosencephaly?
some posterior separation but mostly fused
What is alobar holoprosencephaly?
complete failure of hemispheric division with one lateral ventricle
