Neuro-Surgery Delta Flashcards
What level does the spinal cord begin and end at?
Begins at the medulla oblongata and ends at L1-2 to form the cauda equina
Describe the spinal cord in terms of where the white and grey matter is
Gray matter H-shape, surrounded by white matter
Which horns receive somatosensory information
Dorsal (posterior) horns
Which horns contain motor neurons for muscle innervation
Ventral (anterior) horns
When are lateral horns present and what is their function
T1-L2
Contain autonomic sympathetic neurons
What is the central canal
Cerebrospinal fluid-filled space that runs longitudinally through the length of the entire spinal cord
What are the three main ascending tracts
Dorsal Column-Medial Lemniscus tract (DCML)
Spinothalamic tract
Spinocerebellar tract
What information does the DCML pathway transmit
Fine touch, pressure, and vibration
What information does the Spinothalamic tract transmit
Pain and temperature
What information does the Spinocerebellar pathway transmit
Unconscious proprioceptive information to the cerebellum
What is the function of the Spinocerebellar tract
To help coordinate posture and the movement of the lower limb and upper limb musculature.
What is the gracile fasciculus
The part of the DCML pathway which transmits information from T6 and below
Lies medially
What is the other fasciculus apart from gracile
Cuneate Fasciculus
Transmits information from upper trunk and arms (above T6)
Lies more laterally
Where do the DCML fibres decussate
Medulla
decussate to the contralateral medial lemniscus
Where do DCML fibres go after the medial lemniscus
Synapse at thalamus
Then signals are relayed via the internal capsule to the primary somatosensory cortex
What is located at the precentral gyrus
Primary somatomotor cortex
Where do spinothalamic tract fibres decussate
At a segmental level as they enter the spinal cord
Which tract do spinothalamic fibres go through before synapsing at the dorsal horn
Tract of Lissauer
What are the 2 main pyramidal tracts
Corticospinal tract
Corticobulbar tract
Name the 4 main extra-pyramidal tracts
Vestibulospinal
Rubrospinal
Reticulospinal
Tectospinal
What is the difference between the pyramidal and extrapyramidal tracts
Pyramidal tracts control voluntary movements and originate from the primary somatomotor cortex
Extrapyramidal tracts control involuntary movements and originate from the brainstem
Where do all the corticospinal tract fibres decussate
85% of the corticospinal tract fibres decussate at the medullary pyramids where they become the lateral corticospinal tract
The other 15% travel down via the anterior corticospinal tract and decussate at a spinal level via the anterior white commissure
What muscles does the lateral corticospinal tract innervate
The distal extremities
What muscles does the anterior corticospinal tract innervate
Proximal and axial muscles
What is the function of the corticobulbar tracts
Contain the upper motor neurone of the cranial nerves, to provide innervation of the face, head and neck. They innervate cranial motor nuclei bilaterally
Two exceptions are the hypoglossal nuclei and lower facial nuclei which are innervated contralaterally only
What is the clinical significance of the corticobulbar tracts
An upper motor lesion affecting the facial nerve causes paralysis of the lower half of one side of the face only and the forehead muscles remain unaffected
a lower motor neurone lesion would cause a paralysis of the ipsilateral one-half of the face including the forehead (Bell’s palsy)
Where does the vestibulospinal tract originate and what is it’s function
Originates from the vestibular nucleus in the pons
Controls balance and posture by innervating the anti-gravity muscles
What are the anti-gravity muscles
Extensors in the lower limbs and flexors in the upper limbs
Where does the reticulospinal tract originate
Originates from the reticular formation in the medulla and pons
What is the difference in function between the pontine and medullary reticulospinal tract
Pontine - facilitates reflexes + increases tone
Medullary - inhibits reflexes + decreases tone
Where does the rubrospinal tract originate and what is its function
Originates from the red nucleus(in midbrain)
Excites flexors and inhibits extensors
Where does the tectospinal tract originate and what is its function
Originates from the superior colliculus in the midbrain
Co-ordinates movements of head and neck to vision stimuli (think ecto)
What are the 2 parts of the intervertebral discs called
Outer Annulus Fibrosus
Inner Nucleus Pulposus
Which ligament connects the anterolateral aspects of vertebral bodies and IV discs
Anterior longitudinal ligament
Which ligament runs within the vertebral canal posterior to the vertebral bodies
Posterior longitudinal ligament
Which ligament helps maintain an upright posture and assists straighten the spine after flexion
Ligamentum Flavum
Where does the Ligamentum Flavum run
Runs vertically connecting the lamina of adjacent vertebrae
Where does the supraspinous ligament run
Along the tips of the spinous processes
Where does the interspinous ligament run
Between the spinous processes
What can occur when facet joints are hypertrophied
Patients get referred pain from the nerve supplying the facet joint that mimics sciatica
What is the difference between facet joint referred pain and sciatic pain
Facet joint referred pain does not spread below the knee
What are red flags for lower back pain
Age: >60 or <20 years old Pain not improved by rest Pain that wakes the patient up at night Urinary retention/incontinence and faecal incontinence Saddle anaesthesia History of malignancy Unexplained weight loss. Fever, immunosuppression or IV drug abuse
Which nerve root is being compressed if there is pain along the posterior thigh with radiation to the heel
S1
Which nerve root is being compressed if there is weakness of dorsiflexion of the toe or foot
L5
Which nerve root is involved if there is wasting of the quadriceps muscle and a reduced knee-jerk
L4
What urgent investigations must be performed in suspected cauda equina
MRI lumbosacral spine
PR exam to check anal tone
Which cord syndrome would cause a “cape-like” spinothalamic sensory loss
Central cord syndrome
Why is there predominantly bilateral upper limb weakness rather than lower limb weakness in central cord syndrome
Fibres supplying the upper limbs in the lateral corticospinal tracts are more medial to the fibres supplying the lower limbs
Which part of the body will lose its dorsal column input in central cord syndrome
None
The DCML pathway is typically preserved in central cord syndrome
What might cause anterior cord syndrome
Cord infarction by the area supplied by the anterior spinal artery
What is the presentation of anterior cord syndrome
Paralysis and loss of pain and temperature below the level of injury with preserved proprioception and vibration sensation
What is the presentation of Brown-Sequard syndrome
Ipsilateral loss of motor function and proprioception below the lesion
Contralateral loss of pain and temperature below the lesion
Name the 6 lobes of the cerebral hemispheres
Frontal Temporal Parietal Occipital Insular Limbic
Damage to which area results in expressive aphasia
Broca’s area
What is expressive aphasia
When a patient can understand a language but cannot produce it properly
Where is Broca’s area found
Inferior frontal gyrus
Which lobes contain the pre and postcentral gyri
Precentral gyrus –> Frontal lobe
Postcentral gyrus –> Pareital lobe
Which structure separates the frontal and parietal lobes
Central sulcus
Which structure separates the parietal and temporal lobes
Lateral fissure (Sylvian fissure)
Which structure separates the frontal and temporal lobes
Lateral fissure (Sylvian fissure)
Which lobe contains the primary visual cortex
Occipital lobe
Which structure separates the parietal and occipital lobes
Parieto-occipital sulcus
Damage to Wernicke’s area would cause which condition
Receptive aphasia
What is receptive aphasia
When a patient can produce words and sentences properly but has impaired comprehension of a language
Where is Wernicke’s area located
Superior temporal gyrus
What is a pneumonic for remembering the parts of the limbic system
Hippo with a HAT
What does Hippo with a HAT stand for
Hippocampus
Hypothalamus
Amygdala
Thalamus
What are the 3 components of the cerebellum
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
What is the function of the Vestibulocerebellum
Receives input from the vestibular organs for the maintenance of balance and coordinating vestibule-ocular reflexes
What is the function of the Spinocerebellum
Maintains muscle tone and participates in posture and gait
What is the function of the Cerebrocerebellum
Coordination of voluntary motor activity and correct any error in the movements
Name the parts of the basal ganglia
Caudate nucleus Putamen Globus pallidus Subthalamic nucleus Substantia nigra
What are the 3 layers of the cerebellum
Molecular layer (outer)
Purkinje cell layer (middle)
Granule cell layer (inner)
Where do afferent projections come into the cerebellum
Granule cell layer
Where do efferent projections from the cerebellum originate from
Purkinje cell layer
Which common disease affects the pars compacta of the sunstantia nigra
Parkinson’s
What is the triad associated with Parkinson’s
Rigidity (cogwheel)
Brady/Akinesia
Resting (pill rolling) tremor
What are the three main arteries supplying the brain’s anterior circulation
Internal carotid
Anterior cerebral
Middle Cerebral
Where does the internal carotid artery originate
Bifurcates from the common carotid
Where does the internal carotid terminate
Terminates into a bifurcation as the middle cerebral artery and anterior cerebral artery
Which artery is larger, the anterior cerebral or the middle cerebral
Middle cerebral
Where do the anterior and middle cerebral arteries originate
From the bifurcation of the internal carotid
How are the right and left anterior cerebral arteries connected
Via the anterior communicating artery
Which 4 arteries make up the posterior circulation
Vertebral artery
Basilar artery
Posterior cerebral artery
Posterior communicating artery
Where does the vertebral artery originate
Arises from the subclavian artery and extends through the transverse foramen of the cervical vertebrae
What do the right and left vertebral arteries join to make
The basilar artery
What is the origin of the basilar artery
Arises from the two vertebral arteries joining
What is the origin of the posterior cerebral artery
Arises from the termination of the basilar artery
What is the origin of the posterior communicating artery
Arises from the internal carotid artery
What is the function of the posterior communicating artery
Connects the anterior and posterior circulations
What are the 2 divisions of the venous system of the brain
Cerebral veins
Dural venous sinuses
What are the dural venous sinuses
Large venous channels that are contained within the dura which contain arachnoid granulations, allowing CSF to be absorbed
What is the function of the cerebral veins
Cerebral veins drain blood into the sinuses
What is the difference between the superficial and deep cerebral veins
Superficial veins mainly drain into the superior sagittal sinus
Deep veins mainly drain into the straight sinus
What is a typical presentation of a subarachnoid haemorrhage
Sudden onset of a thunderclap headache
Which symptoms may be present due to any cause of meningeal irritation
Neck stiffness
Photophobia
A third nerve palsy would suggest an aneurysm in which vessel
Posterior communicating artery
How is the diagnosis of subarachnoid haemorrhage made
CT scan
What would a lumbar puncture, performed a few hours after a subarachnoid haemorrhage, show
Xanthochromia
A yellow discolouration of the CSF
What is the most common electrolyte disturbance which can occur after a subarachnoid haemorrhage
Hyponatraemia
What are the 4 types of stroke
Lacunar infarct
Total Anterior Circulation Infarct
Partial Anterior Circulation Infarct
Posterior Circulation Infarct
How is a lacunar infarct defined
A pure motor or pure sensory stroke or an ataxic hemiparesis
Which 3 symptoms must be present to classify a stroke as a Total Anterior Circulation Infarct
- Higher cerebral dysfunction (e.g. dysphasia).
- Homonymous visual field defect
- Ipsilateral motor and/or sensory deficit of at least two areas (out of the face, arm and leg)
What is the difference between a Total and Partial Anterior Circulation Stroke
Partial only requires 2 out of 3 of:
- Higher cerebral dysfunction (e.g. dysphasia).
- Homonymous visual field defect
- Ipsilateral motor and/or sensory deficit of at least two areas (out of the face, arm and leg)
A Posterior Circulation Infarct must have one of which four symptoms
- Ipsilateral cranial nerve palsy with contralateral motor and/or sensory deficit
- Bilateral motor and/or sensory deficit
- Cerebellar dysfunction
- Isolated homonymous visual field defect
Where is the oculomotor nucleus located
In the dorsal midbrain at the level of the superior colliculus
Where is the trochlear nucleus located
In the midbrain at the level of the inferior colliculus
Which nerve travels through the cavernous sinus and where is its nucleus located
Abducens nerve
The nucleus is in the pontine tegmentum
What is the pathophysiology of optic neuritis
Inflammation of the optic nerve
Which two types of diseases can cause optic neuritis
Infective or demyelinating
What is Charcot’s triad with regard to Multiple Sclerosis
Nystagmus
Intention tremor
Staccato speech
What is L’Hermitte’s sign
Electrical shock sensation on neck flexion
What is the Uhthoff phenomenon and which disease is it seen in
Worsening of symptoms due to increase in temperature, such as exercising or hot shower
Seen in MS
What is a treatment for optic neuritis
Intravenous methylprednisolone followed by oral prednisolone
What 3 drugs can be used for MS (not symptomatic treatment)
Interferon beta
Copaxone
Tecfidera
What is the pathophysiology of Myasthenia gravis
Autoimmune disease of acetylcholine receptors at post-synaptic neuromuscular junctions
How can myasthenia gravis typically present
Muscle fatiguability of:
Extraocular muscles
Facial muscles
Bulbar muscles
What is the Cogan Lid twitch and which disease is it seen in
Brief upshoot of the lid elicited by making patient look downwards then upwards
Seen in ocular myasthenia gravis
What is the ice test and what disease is it used to check for
Ptosis improve after applying ice to upper eyelid for 2 mins
Myasthenia gravis
How does the ice test work in Myasthenia Gravis
The cold decreases the acetylcholinesterase break-down of acetylcholine at the NMJ, allowing more to accumulate and increasing muscle contraction
What is the treatment of Myasthenia Gravis
Pyridostigmine (anticholinesterase)
Hyperplasia of which body part is associated with Myasthenia Gravis
Thymus
What does decorticate posturing suggest
Indicates severe brain damage where the midbrain is spared
What is decorticate posturing
The patient presents with abnormal flexion of his arms, the hands are clenched into fists, and the legs extended and feet turned inward
How does decorticate posturing occur
Lateral corticospinal tracts are disrupted so the rubrospinal tracts take over causing the abnormal flexion to the upper extremities and the reticulospinal tracts take over causing the extension of the legs
What is decerebrate posturing
The patient presents with his head arches back and both arms and legs extended
What does decerebrate posturing suggest
Indicates an even more severe brain damage and brainstem damage, specifically at a level below the red nucleus in the midbrain
How does decerebrate posturing occur
Both the lateral cortical spinal tract and rubrospinal tract are damage so the reticulospinal tract takes over and causes extension of the whole body
Which type of haematoma is the accumulation of blood in a space between the dura and the bone
Extradural Haematoma
What is the most common source of bleeding in an extradural haematoma
Middle Meningeal artery
What appearance will an extradural haematoma have on a CT scan
A lens-shaped appearance
Which vessels rupture during a Subdural Haematoma
Bridging veins (veins which drain the cortex and empty into dural sinuses)
How can chronic subdural haematomas occur
Brain atrophy due to alcoholism, age or dementia
How do acute subdural haematomas show up on CT
A crescent-shaped hyperdensity representing acute blood products
How do chronic subdural haematomas show up on CT
A hypodense crescent-shaped appearance
