Week 4 Flashcards
What does the acronym SCALP stand for?
Skin
Connective tissue (dense, fibrous and fatty, blood vessels and nerves)
Aponeurosis (galea aponeuortica, from frontalis to occipitalis)
Loose connective tissue (collagen I and II in random layers)
Periosteum/pericranium (nutrients and repair)
Why is the aponeurosis of the skull clinically important?
Laceration through the aponeurosis = loss of anchoring of superficial layers, wide gaping wound needing sutures
Laceration not though aponeurosis = glue can be used
What 2 portions can the skull be divided into?
Vault and base
How is the skull designed to withstand a blow to the head?
Convex shape allows distribution of force to prevent fracture
What type of injury is caused by a hard blow to the skull?
Depressed skull fracture
What is a linear fracture?
Fracture at site of impact on vault with fracture lines radiating away
What type of fracture may take hours to present?
Base of skull fracture
How does a base of skull fracture present?
Bruising over mastoid process may be only initial sign; over time panda/raccoon eyes bruising is seen
What is the pterion?
The thin bony region where the frontal, parietal and temporal bones meet at the side of the skull
What major blood vessel lies near to the pterion and why is this clinically important?
Middle meningeal artery branches
At risk of intracranial bleeding as the bone is thin here
What are the 2 layers of the dura mater?
Periosteal layer - adheres to surface of cranium
Internal meningeal layer - continuous except at sinuses and reflections
What are the types of intracranial haematoma?
Extra/epidural haematoma
Subdural haematoma
Intracerebral haematoma
Explain the origin and distribution of epidural haematomas
Arterial bleeding from middle meningeal artery collects between periosteal layer of dura and skull
Blood strips dura away from periosteum but periosteum is fixed at point of sutures which stops blood spreading around whole skull
Explain the origin and distribution of subdural haematomas
Venous blood between dura and arachnoid junction
No limitation of flow so blood spreads more thinly
Why might an extradural haematoma be difficult to image on CT?
White blood can turn grey after some time, which makes it more difficult to differentiate from brain matter
What are the CT features of an extradural haematoma?
Characteristic lens shape of blood
Midline shifted away from blood
Swelling obstructs ventricles on the same side
What are the CT features of a subdural haematoma?
Thinly spread blood around brain circumference in crescent shape
Midline shift and swelling
What does the Monroe-Kellie principle dictate?
Intracranial volume is constant
How can volume expansion in the cranial cavity be compensated for?
CSF can displace small amount into spinal theca and venous system via arachnoid granules (75ml)
Intracranial blood can redistribute peripherally in a small amount (75ml)
What volume of mass will cause a rapid increase in ICP and what is this called?
100-120ml
Critical point
What 2 factors are not involved in compensation as they are fixed?
Brain volume (incompressible) Arterial volume (blood flow to brain is constant)
How does ICP affect cerebral perfusion pressure?
Blood moves from high to low pressure
Raised ICP decreases the pressure gradient which normally favours blood flow to the brain
What is cerebral perfusion pressure measurement used for medically?
Surrogate marker of blood flow to the brain
What is the formula linking cerebral blood flow, mean arterial pressure and intracranial pressure?
CPP = MAP - ICP
How does the brain normally maintain a constant blood flow?
Autoregulation of blood flow to brain independent of MAP by altering resistance of cerebral vessels
How is ICP monitored?
Neurological observations chart every 15 minutes - GCS, vital signs (pulse, temp), pupil response, motor/sensory response
What are the signs of increasing ICP?
Decreasing Glasgow Coma Scale score
Diminished pupil response to light
Lateralising signs
Briefly describe various stages of brain herniation
Displacement of cingulate gyrus to opposite side under falx cerebri (asymptomatic/drowsy/confused/weak) Brain moves downwards; uncus is squashed against midbrain which compresses oculomotor nerve (fixed, dilated pupil and then down and out) Brainstem compression (coma)
What is the Glasgow coma scale and what are its components?
Clinical assessment of consciousness
Check, observe, stimulate and rate the response - eyes, verbal, motor
How are the eyes, verbal and motor components of the GCS scored?
Eyes - spontaneous, to sound, to pressure, none
Verbal - orientates, confused, words, sounds, none
Motor - obeys commands, localising, normal flexion, abnormal flexion, extension, none
How is the olfactory nerve tested?
With eyes closed and one nostril plugged, ask the patient to identify a familiar smell; test the other nostril with a different smell
Can also just ask the patient if there has been any changes to their sense of smell
How is the optic nerve tested?
Visual acuity
Visual fields
Pupil reflexes
Fundoscopy
How are the oculomotor, trochlear and abducens nerves tested?
Ask the patient to follow the movement of your finger with their eyes as you trace a letter H in the air in front of them
How is the trigeminal nerve tested?
Sensory - ask the patient to close their eyes, touch them lightly in various areas with a cotton wool ball and ask them to let you know when they can feel it
Motor (masseter and temporalis) - place your fingertips on the patient’s temples and then jaw, asking them to clench their teeth each time
Jaw jerk reflex
Corneal reflex
How is the facial nerve tested?
Ask the patient to raise their eyebrows, frown, smile and puff out their cheeks as well as asking them to close their eyes tightly and resist your attempts to open them
How is the vestibulocochlear nerve tested?
Stand behind the patient and whisper numbers which they should repeat
Hold a ticking watch from a distance and bring it slowly towards the patient until they can hear it
Rinne’s and Weber’s tests for hearing loss
How is Rinne’s test conducted?
Place a sounding tuning fork on the patient’s mastoid process and the next to their ear and ask which is louder (ear should be louder)
How is Weber’s test conducted?
Place the tuning fork base down on the centre of the patient’s forehead and ask if it is louder in either ear (should be equal)
How is the vestibular portion of the vestibulocochlear nerve tested?
Not usually tested in routine cranial nerve exam
How is the glossopharyngeal nerve tested?
Gag reflex
How is the vagus nerve tested?
Ask the patient to say “aah” and check their uvula for deviation
Normal speech is also indicative of functioning vagus nerve
How is the accessory nerve tested?
Ask the patient to turn their head whilst you apply resistance with your hand on their cheek (sternocleidomastoid)
Place your hands on the patient’s shoulders and ask them to shrug while you apply resistance (trapezius)
How is the hypoglossal nerve tested?
Ask the patient to stick out their tongue and check for fasiculations, deviation or wasting
What nerve supplies sensory innervation for touch and temperature to the nasal cavity?
Trigeminal nerve
What areas of the eye are under parasympathetic control?
Constrictor pupillae
Ciliary muscle
What are the afferent and efferent nerves involved in the corneal reflex?
Afferent - trigeminal
Efferent - facial
What nerves supply taste innervation to the tongue?
Facial nerve anterior 2/3
Glossopharyngeal posterior 1/3
What are the afferent and efferent nerves involved in the gag reflex?
Afferent - glossopharyngeal
Efferent - vagus
Where is a berry aneurysm likely to be found?
Circle of Willis
What cognitive processes can attention be subdivided into?
Arousal
Vigilance
Divided attention
Selective attention
What is an example of a domain-specific cognitive process?
Spatial awareness
What is attention?
A global cognitive process encompassing multiple sensory modalities, operating across sensory domains
What is the result of a breakdown in global attention?
Delirium/acute confusional state
What is the result of impaired arousal?
Drowsiness
What is the result of impaired vigilance?
Impersistence (inability to sustain simple voluntary acts)
What is the result of impaired divided or selective attention?
Distractible (easily distracted)
What parts of the brain are involved in inattention/neglect?
Prefrontal, parietal and limbic cortex
What part of the brain is involved in drowsiness/delirium/coma?
Ascending reticular activating system (ARAS)
What is the ARAS?
Ascending reticular activating system - set of connected nuclei in the brain responsible for regulating wakefulness and sleep-wake transitions
What is top-down modulation?
Ability to direct attention toward encountered stimuli based on our goals
What is bottom-up modulation?
Ability to direct attention based on stimulus characteristics (e.g. novelty or salience)
What cortical areas are involved in top-down modulation?
Prefrontal cortex
Parietal cortex
Limbic cortex
What is the limbic system?
A complex brain network which controls basic emotions (fear, pleasure, anger) and drives (hunger, sex, dominance, care of offspring)
What are the components of the limbic system?
Cingulate gyrus, hippocampus, fornix, amygdala, orbital cortex, prefrontal cortex, mamillary bodies
What brain area is involved in bottom-up regulation?
ARAS
What does the ARAS consist of?
Brainstem nuclei, thalamic nuclei, cortex
What clinical tests are there for attention?
Orientation in time and place
Serial 7s (counting down from 100 in 7s)
Digit span and backwards
Months of the year/days of the week in reverse order
Alternation tasks
Stroop test (saying different coloured words)
Star cancellation test
What are the 2 types of memory?
Long-term and immediate/working
What are the 2 types of long-term memory?
Explicit/declarative
Implicit/procedural
What are the 2 types of explicit/declarative memory?
Episodic and semantic
What are the 2 types of implicit/procedural memory?
Motor skills and classical conditioning
What is immediate/working memory?
Immediate recall of small amounts of verbal or spatial information
What area of the brain is involved in central executive function of memory?
Dorsolateral prefrontal cortex
What is episodic memory?
A form of explicit/declarative memory
Personally experienced, temporally specific episodes/events
What is the circuit of Papez/medial limbic circuit?
Neural circuit for the control of emotional expression involving medial temporal lobe (hippocampus, entorhinal cortex) and diencephalon (mamillary bodies, thalamic nuclei)
What neural networks/areas are involved in episodic memory?
Circuit of Papez
Dorsolateral prefrontal cortex
What are acute causes of episodic memory impairment?
Pure amnesia - transient global amnesia, transient epileptic amnesia
Mixed deficit - delirium
What are the chronic causes of episodic memory impairment?
Pure amnesia - hippocampal damage (HSV, Alzheimer’s), diencephalic disease (thalamic stroke, sub-arachnoid haemorrhage)
Mixed deficit - dementia
How can episodic memory be tested?
Recall of complex verbal information (e.g. recall of stories in the Wechsler Memory scales)
Word-list learning (e.g. California verbal learning test)
Recognition of newly encountered words and faces (Warrington’s recognition memory test)
Recall of geometric figures (e.g. Rey-Osterrieth Figure test)
What is semantic memory?
A form of explicit/declarative memory Factual information (general knowledge) and vocabulary
What is the proposed anatomy of semantic memory?
Information is initially processed via episodic memory systems – after repeated rehearsal gets transferred to semantic storage structures
What brain areas are involved in semantic memory?
Left hemisphere anterior temporal lobe
Anterior temporal cortex
Angular gyrus
What is meant by category-specific semantic memory?
Theoretical ‘gradients’ of different semantic processes arranged anatomically
Ventral (visual) to dorsolateral (non-visual)
Posterior (basic objects) to anterior (complex)
What can cause semantic memory impairment?
Anterior temporal cortical destruction/atrophy - HSV, trauma, tumours
What is prosopagnosia and what type of memory is affected?
Neurological disorder characterised by the inability to recognise faces
Semantic memory
How can semantic memory be tested?
Tests of general knowledge and vocabulary (e.g. Wechsler Adult Intelligence Scale)
Fluency (generate exemplars from specific semantic categories e.g. name as many animals as possible in 60 secs)
Object naming to confrontation (e.g. Boston naming test)
Tests of verbal knowledge (e.g. what colour is a banana?)
Person-based tasks (e.g. naming photographs of famous people)
What types of memory are available to conscious access and reflection?
Episodic and semantic
What type of memory is not available to conscious access and reflection?
Procedural memory
What is procedural memory?
Ability to acquire motor skills required to perform certain tasks (e.g. playing a musical instrument)
What is Korsakoff’s syndrome?
A chronic memory disorder caused by severe deficiency of thiamine
What brain areas are involved in procedural memory?
Basal ganglia and cerebellum
How is procedural memory tested?
Cannot be done at bedside
What are the components of sensory memory?
Iconic (sight)
Echoic (hearing)
Haptic (touching)
What are the components of working memory and what are they responsible for?
Visual sketchpad - spatial information
Phonological store - words, numbers, melodies
What part of the brain is responsible for integrating the visual sketchpad and phonological store information in working memory?
Central executive - dorsolateral prefrontal cortex
How does the bony palate contribute to the nasal cavity?
Floor
What is the soft palate made of?
Fibrous tissue and skeletal muscle
What is the nasal septum made of?
Cartilage and bone
What type of cartilage is the epiglottis composed of and what colour is it?
Elastic
Yellow
What are the boundaries of the nasopharynx?
From end of nasal septum to end of soft palate
What are the divisions of the pharynx in order?
Nasopharynx
Oropharynx
Laryngopharynx
What are the 2 mucosal folds found in the pharyngeal area and what are they associated with?
Palatoglossal and palatopharyngeal folds
Muscles of the same name
Where is the palatoglossal fold found?
Where the oral cavity becomes the oropharynx
Where is the palatopharyngeal fold found?
End of soft palate
What marks the boundary between the oro and laryngopharynx?
Tip of the epiglottis
What 2 recesses are found in the pharyngeal area?
Piriform fossa and pharyngeal recess
What is the clinical importance of the piriform fossa?
Shallow area where fish-bones have a propensity to get stuck
What is the anatomical position of the piriform fossa?
Near inlet to larynx
What is the anatomical position of the pharyngeal recess?
Passes behind the auditory tube, near the passage of the internal carotid artery
What is the pharyngeal recess also known as?
Fossa of Rosenmuller
Where does the auditory tube open?
Side wall of nasopharynx
What is the tubal elevation?
Raised area around the opening of the auditory tube
What is the tubal tonsil?
Lymphoid tissue found above and behind the tubal elevation
Where is the pharyngeal tonsil and by what name is it commonly referred?
Upper back wall of nasopharynx
Adenoid
What tonsil is commonly referred to as the adenoid?
Pharyngeal tonsil
Where is the palatine tonsil?
Between palatoglossal and palatopharyngeal folds
Which tonsil is visible on opening the mouth and depressing the tongue?
Palatine tonsil
What is Waldeyer’s ring?
Interrupted ring of tonsil tissue near the start of the respiratory tract which provides protection
What is glue ear?
Chronic otitis media with effusion; result of recurrent throat infection with antibiotic treatment which can lead to hypertrophy of tubal tonsil and subsequent blockage of the auditory tube
Which tonsil is implicated in glue ear?
Tubal tonsil
How do ventilation tubes work in treatment of glue ear?
Allows air to enter the inner ear which causes mucus to be resorbed; falls out after a few months
What position does the ear need to be in to examine with an auriscope and why?
Pinna must be pulled up and back to straighten the external auditory meatus
What is the umbo of the tympanic membrane?
Concave part
What is the cone of light of the tympanic membrane?
Light reflection of auriscope
What is the pars tensa of the tympanic membrane?
Three layered area (skin, fibrous, mucosa) which is most commonly associated with perforations
What are the 3 types of fibres in the middle fibrous layer of the pars tensa of the tympanic membrane?
Radial
Circular
Parabolic
What does the middle fibrous layer of the pars tensa of the tympanic membrane enclose?
Handle of malleus
What is the pars flaccida of the tympanic membrane?
Fragile, two-layered upper region associated with auditory tube dysfunction and cholesteatomas
What is a cholesteatoma?
An abnormal, non-cancerous skin growth in the middle ear; birth defect or caused by repeated middle ear infections
What are ceruminous glands?
Specialised apocrine sweat glands located subcutaneously in the external auditory canal, in the outer 1/3; inner secretory cells and outer myoepithelial cells
What does the auditory canal connect?
Pharynx and middle ear cavity
What are the middle ear ossicles?
Malleus (hammer)
Incus (anvil)
Stapes (stirrup)
Where are the middle ear ossicles located?
In the tympanic cavity
How is sound amplified in the ear?
Tympanic membrane is 20x bigger than the footplate of the stapes bone
What holds the footplate of the stapes in place at the fenestra vestibuli?
Annular ligament
What aspect of the ear can become calcified in old age, leading to hearing loss?
Annular ligament
In the ear, what is the attic?
Area of tympanic cavity above the level of the tympanic membrane
What is the mastoid antrum?
Air space in the petrous portion of the temporal bone
What muscles are present in the ear to stabilise the ossicles and protect the ear?
Tensor tympani muscle (supplied by CN 5) and stapedius muscles (CN 7)
How are traumatic brain injuries classified?
Mild (GCS >12)
Moderate (GCS 9-12)
Severe (GCS <9)
What 2 types of head injury are there? Give examples
Focal (e.g. scalp, skull, intracranial haemorrhage, brain contusion)
Diffuse - diffuse axonal injury, ischaemia, swelling
What blood vessels are most commonly associated with extradural haematomas?
Middle meningeal arteries
What blood vessels are most commonly associated with subdural haematomas?
Bridging veins
What brain lobes are most commonly affected by intracranial haematoma?
Frontal or temporal
Which type of TBI has a lucid interval and rapid deterioration?
Extradural haematoma
What type of TBI has a gradual deterioration?
Subdural haematoma
What type of haemorrhage is associated with a contusion?
Subarachnoid haemorrhage
What is a diffuse axonal injury?
Axonal damage due to shear forces on acceleration/deceleration; present in all severities of TBI
What brain matter is affected by DAI?
White matter of corpus callosum and dorsolateral brainstem
How does brain ischaemia occur in TBI?
Consequence of raised intracranial pressure, hypoxaemia and reduced cerebral perfusion pressure
What is a diffuse vascular injury?
Multiple small haemorrhages of the cerebral hemispheres/brain stem resulting in death within minutes of injury
What is concussion?
Mild traumatic brain injury; a (temporary) disturbance in brain function as a result of trauma
What are the symptoms of concussion and when do they appear?
Headache, dizziness, memory disturbance, balance problems, ‘seeing stars’
Onset may be delayed
What are the risk factors for concussion?
History of previous concussion, artificial pitches, gumshield, female sex, helmet/headgear, age <18
What is second impact syndrome?
Occurs when the brain swells rapidly due to a concussion only minutes/days/weeks after an initial concussion, before symptoms have subsided
What is sub-concussion?
Hits below the concussion threshold; the brain is shaken, but not so violently that the damage to brain cells is severe enough to see symptoms
What is punch-drunk syndrome?
Chronic traumatic encephalopathy
A condition seen in boxers and alcoholics, caused by repeated cerebral concussions
What are the characteristics of punch-drunk syndrome/chronic traumatic encephalopathy?
Weakness in the lower limbs Unsteadiness of gait Slowness of muscular movements Hand tremors Hesitancy of speech and mental dullness
What is the effect of chronic traumatic encephalopathy on the brain?
Septal and hypothalamic (cavum septum, fornix and mamillary bodies atrophied)
Cerebellar (tonsillar scarring, reduction in Purkinje cells)
Substantia nigra (loss of pigment)
Neurofibrillary tangles
Amyloid plaques
What is declarative memory?
Episodic and semantic
Factual information, life events
Available to consciousness, easily formed/forgotten
What is non-declarative memory?
Procedural
Skills and habits, classical conditioning
Not available to consciousness, less easily formed/forgotten
What 2 strategies are involved in the control of voluntary movements?
Ballistic/pre-programmed
Pursuit/visual feedback
What are ballistic movements? Give an example
Movements based largely on a set of pre-programmed instructions
Rapid but at expense of accuracy (little opportunity for compensation for unexpected changes)
E.g. striking a cricket ball, returning a tennis serve
What are pursuit movements? Give an example
Motor command continually updated according to sensory feedback (e.g. visual)
Highly accurate (can be modified while in progress) but slow
E.g. visual tracking
What areas of the cortex are involved in voluntary movement?
Area 6 - SMA, PMA
Area 4 - M1
Area 5 and 7 - posterior parietal cortex
What types of sensory information are crucial for control of movement?
Proprioception - somatic sensory cortex
Vision - eyes, visual system and visual cortex
Vestibular - feedback from organs of balance
How does stroke affect movement?
Paralysis and loss of sensation on contralateral side to haemorrhage
What area of the brain is involved in rehearsal of a movement before it is carried out?
Supplementary motor area (SMA)
What are the main non-cortical brain structures involved in control of movement?
Basal ganglia and cerebellum
What is the function, input and output of the basal ganglia?
Function - initiation of movement, planning complex movement
Input - prefrontal cortex
Output - thalamus to premotor area
What are the symptoms of Parkinson’s disease?
Tremors, hypokinesia, shuffling gate
Progressing to general cognitive decline
What are the treatments for Parkinson’s disease?
L-DOPA, deep brain stimulation
What are the symptoms of Huntington’s disease?
Choreas, difficulty speaking and swallowing
Progressing to general cognitive decline
What is the function, input and output of the cerebellum (in control of movement)?
Function - co-ordination and smooth execution of movements, motor learning, error detection
Input - sensory cortex
Output - thalamus to primary motor cortex
What lateral pathways are involved in control of movement?
Corticospinal and rubrospinal
Voluntary, distal muscles
What ventromedial pathways are involved in control of movement?
Tectospinal, vestibulospinal, pontine reticulospinal, medullary reticulospinal
Involuntary, axial muscles, posture
What are spinal pattern generators?
Intrinsic circuits of the spinal cord which produce rhythmic motorneuron activity for stepping; alternating, co-ordinated activity in flexor and extensor muscles
How does the circuit for rhythmic alternating activity work?
Two sets of pattern generating neurons project to flexor and extensor motoneurone pools, respectively; reciprocal inhibitory connections between the two sets of pattern generating neurones help to co-ordinate their activity, so that there is alternating excitation of flexors and extensors
What comprises a motor unit?
A motorneuron and the muscle fibres it innervates
What are collections of motoneurons in the ventral horn called?
Motonuclei
How is strength of muscle contraction graded?
By recruitment of motorneurons
