Neuro anatomy Flashcards
What is meant by the dominant and non-dominant cerebral hemispheres?
the side of the brain that controls writing and speech is called the dominant hemisphere
the L hemisphere is dominant in over 90% of right handed people, and 60% of left handed people
What is the function of the prefrontal cortex area of the frontal lobe? What are the symptoms of a lesion in this area?
the anterior and orbital parts of the frontal cortex govern personality, emotional expression, initiative and the ability to plan
altered behaviour including social disinhibition, loss of initiative and interest, inability to solve problems with loss of abstract thought and impaired concentration and attention without intellectual or memory decline. This usually occurs with bilateral lesions resulting from head injury, small vessel disease, frontal degenerations e.g. frontotemporal dementias and acute hydrocephalus
What is the role of the cortical micturition centre in the frontal lobe? What are the symptoms of a lesion in this area?
this region lies in the paracentral lobule and is involved in the cortical inhibition of voiding of the bladder and bowel
incontinence
What is the blood supply to the frontal lobe?
anterior cerebral artery–supplies medial surface of the primary motor cortex, which controls the leg
medial cerebral artery–supplies lateral surface of primary motor cortex which controls face and arm
What is hemiplegia and monoplegia?
Monoplegia refers to weakness of one limb (either arm or leg) and hemiplegia refers to weakness of one arm and leg on the same side of body (either left or right side)
Focal seizures arising from the frontal cortex give what presentation?
clonic movements of the contralateral lower face, arm and leg and conjugate deviation of the head and eyes away from convulsing side (i.e. away from side of lesion)
What is the function of the primary somatosensory cortex in the parietal lobe?
located in the postcentral gyrus
PERCEIVES complex somatosensory stimuli from contralateral side of face and body
it received afferent projections via the thalamus from the somatosensory pathway
the fibres are represented in a homonculus, similar to that of the primary motor cortex
What is the role of the language centre in the parietal lobe?
found in dominant hemisphere
pathways within the arcuate fasiculus connect Broca’s area (frontal lobe) with Wernicke’s area (posterior temporal) pass through the inferior parietal region
What is the role of the ‘body awareness’ area in the parietal lobe?
integration of somatosensory, visual and auditory information (mainly non-dominant)–allows awareness of the body and its surroundings, appropriate movement of the body and constructional ability
What are the functions of the parietal lobe?
Somatosensory perception and integration of visual and somatospatial information
interpreting information such as touch, taste, temperature, visual-spatial processing, identifies where body parts are in relation to each other
Give some symptoms of a parietal lobe lesion
discriminative sensory impairment of the opposite side of the face and limbs–impairment of joint position sense. Pain, temp, vibration and touch are intact
visual disturbance
dominant lobe–
Wernicke’s dysphasia (speech is fluent but words are replaced with partly correct words and incorrect words related to word intended- paraphasia)
Gerstmann’s syndrome–inability to differentiate L and R sides of body
bileteral ideomotor and ideational apraxia
constructional apraxia, dressing apraxia, contralateral sensory inattention
Focal seizures of the parietal lobe may manifest as what symptoms?
sensory symptoms on contralateral side of body e.g. pins and needles
dyslexia, dyscalculia
apraxia–inability to carry out complex tasks despite having an intact sensory and motor system
What is the blood supply to the parietal lobe?
middle cerebral artery
What are the functions of the temporal lobe?
Wernicke’s area in dominant hemisphere–comprehension of written and spoken language
auditory and vestibular cortices
limbic system
limbic system–olfactory and taste centre. Memory, learning and emotion
What are symptoms of lesion in temporal lobe?
Wernicke’s area–receptive dysphasia
auditory agnosia–inability to recognise sounds
vestibular dysfunction
olfactory and taste hallucinations
learning difficulties
memory impairment
emotional disturbances
What is the function of the occipital lobe? What symptoms of a lesion in this area?
pereception of vision
contralateral homonymous hemianopia–central vision intact with loss of peripheral vision
cortical blindness
visual agnosia–impairment of recognising faces and objects
What are the structures of the basal ganglia?
The basal ganglia are a group of structures found deep within the cerebral hemispheres. The structures generally included in the basal ganglia are the caudate, putamen, and globus pallidus in the cerebrum, the substantia nigra in the midbrain, and the subthalamic nucleus in the diencephalon. Despite the name, the basal ganglia are not actually ganglia
What is the function of the basal ganglia?
The basal ganglia receive information from the cortex, much of which is sent first to the caudate and putamen (which together are often referred to as the striatum). After the information is processed by the basal ganglia, it is sent back to the cortex by way of the thalamus.
The functions of the basal ganglia in motor control are to facilitate movement and inhibit competing movements. For example, when someone tries to make an intentional movement like reaching for a pencil, the basal ganglia help to facilitate the movement by allowing motor plans associated with that movement (reaching and grasping in this case) to be activated. At the same time, the basal ganglia cause motor plans that might counteract the movement (perhaps flexing in this case) to be inhibited. The result is a smooth and fluid movemen
What are the components of the diencephalon?
The diencephalon is a small part of the brain that is mostly hidden from view when you are looking at the outside of the brain. It is divided into four parts: the epithalamus, thalamus, subthalamus, and hypothalamus. The diencephalon can be found just above the brainstem between the cerebral hemispheres; it forms the walls of the third ventricle. The only part of the diencephalon that can be seen without taking a cross-section of the brain is the bottom-most portion of the hypothalamus.
What is the role of the epithalamus?
The epithalamus consists primarily of the pineal gland and the habenulae. The pineal gland is an endocrine gland that secretes the hormone melatonin, which is thought to play an important role in the regulation of circadian rhythms.
What is the role of the subthalamus?
portion of the subthalamus is made up of tissue from the midbrain extending into the diencephalon. Thus, parts of midbrain regions like the substantia nigra and red nucleus are found in the diencephalon. The subthalamus is also home to the subthalamic nucleus and the zona incerta. The subthalamic nucleus is densely interconnected with the basal ganglia, and plays a role in modulating movement. The zona incerta has many connections throughout the cortex and spinal cord, but its function is still not determined. Several collections of important fibers (e.g. somatosensory fibers) also pass through the subthalamus.
What is the role of the thalamus?
two oval collections of nuclei - make most of the mass of diencephalon.
relay station = almost all sensory information (exception of smell) that proceeds to the cortex first stops in the thalamus before being sent on to its destination.
The structure is subdivided into a number of nuclei that possess functional specializations for dealing with particular types of information. Sensory information thus travels to the thalamus and is routed to a nucleus tailored to dealing with that type of sensory data. Then, the information is sent from that nucleus to the appropriate area in the cortex where it is further processed.
The thalamus doesn’t deal just with sensory information, however. It also receives a great deal of information from the cerebral cortex, and it is involved with processing that information and sending it back to other areas of the brain. Due to its involvement in these complex networks, the thalamus plays a role in a number of important functions ranging from sleep to consciousness.
Clusters of axons in the PNS and CNS are called what?
nerves in PNS
tracts in CNS
What cells are responsible for myelination of axons?
oligodendrocytes in CNS
Schwann cells in PNS
Name the CNS glial cells
ASTROCYTES: structural and metabolic support for neurons. Most abundant. Determine capillary permeability of blood brain barrier. Control chemical movement
- *MICROGLIAL CELLS-**-phagocytosis
- *OLIGODENDROCYTES-**-forms myelin sheath
- *EPENDYMAL CELLS**–line cavities of brain and spinal cord, cilia assist in CSF circulation. Form partially permeable barrier between CSF
What are the roles of astrocytes,
CNS glial cells
astrocytes–structural and metabolic support for neurons. Most abundant. Determine capillary permeability of blood brain barrier. Control chemical movement
What are the roles of microglial cells?
microglial cells–phagocytosis
What are the roles of oligodendrocytes
oligodendrocytes–forms myelin sheath
What are the roles of ependymal cells?
ependymal cells–line cavities of brain and spinal cord, cilia assist in CSF circulation. Form partially permeable barrier between CSF
What are the glial cells of the PNS system?
- *satellite cells–**similar to astrocytes, metabolic and structural support for neurons
- *schwann cells-**-form myelin sheath
What are the roles of the ventral, dorsal and lateral horns of the spinal cord?
ventral–receive info from brains motor cortex, sends it to skeletal muscles to trigger voluntary movement
dorsal–take sensor info and send to brains sensory cortex
lateral–help regulate processes like urination, digestion, HR. Mostly SNS activity
What are the roles of the parts of the brainstem?
basic life sustaining functions e.g. breathing, BP
midbrain– vision, hearing, motor control, sleep wake cycle, consciousness
pons–facial expressions and sensations, body equilbrium, posture
medulla–respiratory centre, swallow, cough, vomit, BP
In the SNS, where are the preganglioninc and postganglionic neurons located?
preganglioninc neurons located in thoracolumbar spinal cord’s intermediate horn (T1-L2). Release ACh
postganglionic neurons–located close to spinal cord.
Paravertebral ganglia (cervical, thoracic, lumbar, pelvic)
Prevertebral (cerlial, superior mesenteric, inferior mesenteric)
Most are adrenergic but some release ACh
In SNS, what type of neurotransmitters are released?
preganglioninc neurons release ACh which bind to nicotinic receptors on post-ganglionic neurons
postganglioninc neurons are usually adrenergic (noradrenaline)
but some are cholinergic but ACh binds to muscarininc, NOT nicotinic receptors on organs
In the PNS, where are the preganglioninc and postganglionic neurons located?
preganglionic–located in brainstem (nuclei of CN III, VII, IX and X) and sacral spinal cord (S2-4)
they release ACh which binds to nicotinic receptors on postganglionic cell bodies
postganglionic neurons are located close to target organs/in target organs.
mostly cholinergic but some release neuropeptides. Effector receptors are muscarinic
What are the terminal branches of the brachial plexus?
MARMU
musculocutaneous
axillary
radial
musculocutaneous
ulnar
What are the roots of the brachial plexus?
C5, C6, C7, C8, T1
How many cranial nerves originate from the midbrain and above, the pons and the medulla?
3 groups of 4
4 from midbrain and above
4 from pons
4 from medulla
remember, a lesion on the brainstem will usually produce ipsilateral cranial nerve defects
What cells keep CSF in motion?
cilia of ependymal cells lining ventricular system
Where is CSF produced?
mostly (80%) by choroid plexus–network of capillaries, modified ependymal cells in ventricles
remaining 20% is made by ependymal cells lining subarachnoid space
CSF leaves the 4th ventricle by way of the…
3 apertures
R aperture of luschka
L aperture of luschka
median aperture of magendie
What is the rbc, WBC, protein and glucose content of CSF?
no rbc
wbc <5/ml
protein <0.5mg/ml
glucose 60-70% of blood levels (2.5-5mmol)
What is a normal opening pressure in a lumbar puncture?
<20cm in water is normal
21-29 intermediate
>30 is high
remember you cannot estimate pressure if patient is sitting up for LP
What are the causes of hydrocephalus?
CSF accumulation in brain–>increased ICP
symptoms: headaches, double vision, poor balance, mental impairment and increased head size in kids, vomiting, sleepy, seizure, downward pointing eyes
causes: birth defects (neural tube, aqueductal stenosis) or acquired.
Meningitis, brain tumour, traumatic head injury, intraventricula hemorrhage and subarachnoid haemorrhage
treat using a shunt
What are the symptoms of idiopathic intracranial hypertension?
Increased intracranial pressure in the absence of a tumor or other etiology seen on imaging.
Symptoms: headache, pulsatile tinnitus, diplopia, papilloedema (risk of blindness), mydriasis (dilated pupils)
more common in young, overweight women, may be associated with cerebral venous sinus thrombosis
What is the treatment of idiopathic intracranial hypertension?
weight loss
repeated lumbar puncture
shunt
acetazolamide–diuretic used to treat altitude sickness
What is a papilloedema?
Optic disc swelling that is caused by increased intracranial pressure due to any cause. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare.
In intracranial hypertension, the optic disc swelling most commonly occurs bilaterally. When papilledema is found on fundoscopy, further evaluation is warranted because vision loss can result if the underlying condition is not treated. Further evaluation with a CT or MRI of the brain and/or spine is usually performed.
What is brain herniation
brain tissue displacement through the skull opening or dural fold due to increased intracranial pressure
What is Cushing’s triad?
hypertension
bradycardia
irregular respirations
physiological nervous system response to increased intracranial pressure (ICP) that results in Cushing’s triad of increased blood pressure, irregular breathing, and bradycardia. It is usually seen in the terminal stages of acute head injury and may indicate imminent brain herniation. It can also be seen after the intravenous administration of epinephrine and similar drugs
Differentiate between encephalitis and meningitis?
meningitis–inflammation of the meninges of the brain (leptomeninges–pia and arachnoid)
encephalitis–inflammation of the brain
can occur together = meningoencephalitis
What are the symptoms/signs of meningitis?
fever, nausea, vomiting, lethargy, irritable, anorexia, headache, muscle/joint ache, respiratory symptoms (cough)
stiff neck, altered mental state, non-blanching rash, bulging fontanelle (infants), photophobia, kernig’s sign, brudzinski sign
coma, paresis, focal neurological deficit, seizure
ask about: recent exposure, recent infection, IV drug use, head trauma, HIV, immunocompromising conditions
What is Bruzinski’s sign?
flexion of the neck with the child supine causes flexion of knees and hips
meningitis
What is kernig’s sign?
After flexing the hip and knee at 90 degree angles, pain and resistance are noted.
What is opisthotonus?
Sustained contraction of the back muscles resulting in arched position
late sign of meningeal irritation and raised ICP
What WBC are found in bacterial meningitis?
neutrophils
all other causes give lymphocytes
What effect does meningitis infection have on WBC, blood glucose, protein and ICP?
WBC increase (higher in viral causes)
glucose decreases to <2/3 of blood level
pressure increases
protein increases >50mg/dl
What are the causative microorganisms of meningitis by age group
Explaining Big Hot Neck Stiffness
infants: E.coli, group B streptococcurs
kids: Haemophilus infleunzae
young adult: Neisseria meningitidis
elderly: Streptococcus pneumoniae
What is the empirical treatment for bacterial meningitis?
cefotaxime or ceftriaxone
dexamethasone
if patient over 55 add in ampicillin or amoxicillin
What is the treatment for meningococcal meningitis?
benzylpenicillin
or cefotaxime or ceftriaxone
or chloramphenicol if allergic to beta lactams
PLUS dexamethasone
What is a brain abscess?
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local (ear infection, dental abscess, infection of paranasal sinuses, infection of the mastoid air cells of the temporal bone, epidural abscess) or remote (lung, heart, kidney etc.) infectious sources, within the brain tissue. The infection may also be introduced through a skull fracture following a head trauma or surgical procedures.
What is the treatment for a brain abscess?
drainage
plus cefotaxine or ceftriaxone
What are symptoms of brain abscesses?
fever, progressively worsening focal neurology, headache, raised ICP while supine, morning vomiting, mental status change, seizure, papilloedema
Differentiate between encephalopathy and encephalitis?
encephalopathy–clinical syndrome of altered mental status manifesting as reduced consciousness, altered consciousness, altered cognition/personality/behaviour
has many causes: infection, metabolic derrangement, trauma etc
encephalitis is inflammation of the brain
List the most common causative organisms of encephalitis
HSV-1 most common
HSV-2
epstein barr, influenza
What is acyclovir?
Aciclovir, also known as acyclovir, is an antiviral medication. It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles.
What is treatment of tension headache according to NICE guidelines
analgesia (NOT opioids)
if consistent or chronic: Pharmacological prophylaxis with low dose amitriptyline (10-75mg daily)For people who do respond — attempt withdrawal of medication if improvement is maintained for 4-6 months. Withdraw if no response
advise about anelgesia overuse
What is treatment of migraine according to NICE?
keep diary–look for triggers
Ensure that women who have migraine with aura are not using combined hormonal contraception, as this is contraindicated.
restrict analgesia to 2 days a week
offer a triptan
sumatriptan
and an antiemetic metoclopramide 10mg or prochlorperazine 10mg
prophlaxis: beta blocker, amitriptyline
What are triptans?
selective serotonin (5-HT1) agonist ex: sumatriptan
structurally similar to serotonin, reduce vascular inflammation, constrict blood vessels. Used in migraine treatment
What are trigeminal autonomic cephalgias?
Trigeminal autonomic cephalalgia (TAC) is the name for a type of primary headache that occurs with pain on one side of the head in the trigeminal nerve area and symptoms in autonomic systems on the same side, such as eye watering and redness or drooping eyelids.
Cluster headache most common type
recurrent pain in trigeminal distribution with autonomic features (eye watering, nasal congesion, red eye)
What is a cluster headache?
severe, unilateral, retro-orbital headache with restlessness, agitation, ipsilateral lacrimation, rhinorrhoea
short lived 15-90 mins but occur frequently and repeatedly (same time each day) in clusters lasting days to weeks
months without symptoms
males more commonly
What is the treatment of a cluster headache?
triptans, oxygen
high dose verapamil (Ca2+ block, up to 960mg/day)
What is a subarachnoid haemorrhage?
bleeding into the subarachnoid space
symptoms: thunderclap headache, vomit, decreased level of consciousness, fever, and sometimes seizures. Neck stiffness or neck pain are also relatively common.
SAH may occur as a result of a head injury or spontaneously, usually from a ruptured cerebral aneurysm.Risk factors for spontaneous cases included high blood pressure, smoking, family history, alcoholism, and cocaine use. Generally, the diagnosis can be determined by a CT scan of the head if done within six hours of symptom onset.
What is cerebral venous sinus thrombosis?
presence of a blood clot in the dural venous sinuses, which drain blood from the brain. Symptoms may include headache, abnormal vision, any of the symptoms of stroke such as weakness of the face and limbs on one side of the body, and seizures.
symptoms: thunderclap headachea
often in female patients on oral contraceptive pill
MRI scan
What is temporal arteritis?
AKA giant cell arteritis due to subacute granulomatous inflammation of the large vessels
closely associated with polymyalgia rheumatica (aches in shoulder, neck and pelvis)
rare <50 years
localised headache
jaw claudication
visual loss
tender temporal arteries
visual loss
urgent treatment with steroids due to risk of blindness