Anatomy and pattern recognition of the central nervous system normal radiographic appearances and pathology

Question 1

What are the functions of the nervous system

Answer 1

• Sensory input
• Integration
• Motor output
• Homeostasis regulation
• Mental activities
• Reflex actions
• Provides an immediate response when required
• Provide a slower, long term response when required through stimulation of endocrine system and release of hormones

Question 2

Overview of the NS

Answer 2

• Central nervous system
• Peripheral nervous system
- Sensory
- Motor
• Somatic
• Autonomic nervous system
Sympathetic
parasympathetic
There are 2 principal cells of the nervous system
• Glia cell
• neurons

Question 3

What is myelin?

Answer 3

• It is a fatty sheath that wraps around the axons of neurons (the bit of the neuron that conducts electrical impulses away from the neuron cells body)
• Composed of lipids and proteins
• Insulates the axons and increases the speed of electrical impulses as they travel along nerve cells.
• Produced by Glia cells
• CNS – oligodendrocytes
• PNS – Schwann cells

Question 4

Neurons

Answer 4

• Sometimes called a ‘nerve cell’
• Is the fundamental structural unit of the nervous system which transmits information throughout the body.
Types of neurons
• Sensory neurons
• Motor neurons
• Interneurons
Special characteristics
• Longevity
• Amitotic
• High metabolic rate

Question 5

Grey and white matter

Answer 5

• Grey Matter – collections of nerve cell bodies and their dendrites
• Nuclei
• Ganglia
• White matter – myelinated fibres – tracts conveying nerve impulses from generation site to target

Question 6

How is a nerve impulse performed?

Answer 6

Membrane potential
• Difference of charges across the plasma membrane
Resting potential
• Resting cells are (-) inside and (+) outside
• Large amounts of Na+ outside the cell and K+
inside
Action potential/impulse
• Rapid reversals in charges across the plasma
membrane
• Caused by the exchange of ions across the
membrane of the neuron
• Threshold level (-55mV) needed to stimulate neurons ALL-OR-NONE principle

Question 7

How are impulses terminated? – termination of neurotransmitter effects

Answer 7

Degradation of neurotransmitter by enzyme
Reuptake of neurotransmitter
Diffusion of neurotransmitter from synapse

Question 8

Synapse: Excitatory or Inhibitory

Answer 8

• Excitatory Synapses and Excitatory Postsynaptic Potentials (EPSPs)
• Inhibitory Synapses and Inhibitory Postsynaptic Potentials (IPSPs)

Question 9

Meninges

Answer 9

• Cover and protect Central Nervous System (CNS)
• Contains Cerebrospinal fluid (CSF)
• Protect blood vessels
• Dura mater – 2 layers of fibrous tissue mostly attached, fibrous outer attached to skull and an inner enclosing the Central Nervous System
• Arachnoid mater– separated from the dural by the sub-dural space and covers the pia mater. Connects to this by web like extensions forming the
sub-arachnoid space. This is a large space filled with CSF and blood vesssels
• Pia mater – innermost layer attaches to the brain

Question 10

Meninges – Dura mater

Answer 10

• Dura mater
• Separation of layers forms:
• Dural partition of brain:
• Falx cerebri, tentorium cerebelli, Falx cerebelli.
• Intracranial venous structures (sinuses) Superior sagittal sinus, inferior sagittal sinus, confluence of sinuses, straight sinus, transverse sinus
• Extradural space between periosteal (outer) layer and bone of skull
• Subdural space between meningeal (inner) layer and arachnoid mater.
Spinal cord
• Extends as a loose sheath from foramen magnum to the 2nd sacral vertebra.

Question 11

Meninges – Arachnoid mater

Answer 11

• Arachnoid mater
• Passes over the convolutions of the brain.
• Merges with the dura mater to at the 2nd sacral vertebra.
• Arachnoid mater separated from :
• Dura mater by subdural space
• Pia mater by subarachnoid space

Question 12

Meninges – Pia mater

Answer 12

• Pia mater
• Connective tissue
• Adheres to brain covering dipping into fissures
• Continues beyond spinal cord with filum terminale
• Sheaths blood vessels
• Fuses to periosteum of the coccyx with dura mater

Question 13

Ventricles

Answer 13

Irregular shaped cavities located within the brain.
• Contain cerebrospinal fluid (CSF)
• CSF: Suspends brain cells – provides buoyancy
and a fluid environment for biochemical activity.
Thus protects and maintains viability.
• CSF is like plasma with less protein and a
different electrolyte composition. It is essential
for brain function, e.g. very sensitive to pH,
affecting breathing and perfusion of blood.
• Consist of defined aspects:
• Left and right lateral ventricles
• Third ventricle
• Fourth ventricle

Question 14

CSF

Answer 14

• Is produced in the choroid plexuses.
• Located in lateral ventricles, 3rd ventricle roof and 4th ventricle
• Clusters of fine capillaries hanging from the
ventricles.
• Ependymal cells filter blood and modify
composition.
• CSF locates between the pia mater and arachnoid mater, within the sub- arachnoid space.
• CSF secreted continuously
• Volume of CSF constant (150 ml)

Question 15

Functions of CSF

Answer 15

• Keeps brain moist.
• Supports and protects brain and spinal cord
•Transports glucose, oxygen and other needed chemicals from blood to neurons and waste product removal

Question 16

The brain structure

Answer 16

Brain structure:
Cerebrum
Diencephalon
• Epithalmus
• Thalamus
• Hypothalamus
Cerebellum
Brain stem
• Midbrain
• Pons
• Medulla oblongata

Question 17

The brain

Answer 17

• Made of conducting nervous tissue ‘neurons’ and supporting connective tissue ‘neuro-glial’ tissue
• Organisation 4 main regions or 3 fore, mid, hind brain
1. Cerebral hemispheres (2 hemispheres)
2. Dicephalon (thalamus and hypothalamus)
3. Cerebellum
4. Brain stem

Question 18

The brain- cerebrum

Answer 18

• Located in the anterior and middle cranial fossae
• Biggest part in two hemispheres left and right divided by a fissure
• 2 hemispheres are connected by a mass of white fibres (corpus callosum)
• Comprises of:
• Outer cortex: grey matter, contains gyri, sulci and fissures
• Inner white matter, containing nuclei (basal ganglia)
• Has 4 main structural ‘lobes’ that are broadly associated with ‘known’ function.
• Frontal
• Parietal
• Temporal
• Occipital

• Function
• 3 main types of activity
Motor
• Primary motor area anterior to central
sulcus
• Brocas area
Sensory perception to central sulcus
• Primary visual area, auditory area, gustatory and olfactory areas
Association (mental activity)
• Prefrontal area

Question 19

Cerebral hemispheres

Answer 19

• Hemispheric lateralisation
•There is a difference in function between the left and right hemispheres
•Left receives somatic sensory signals from and controls muscles of the right side of body
•Right receives somatic sensory signals from and controls muscles of the left side of body
• Normally the left hemisphere: Reasoning, Numerical and scientific skills
• Ability to use and understand sign language, Spoken and written language
•Normally right: Musical and artistic awareness, Space and patter perception
•Recognition of faces and emotional content of facial expression, Generating emotional
content of language

Question 20

Deeper white matter

Answer 20

• Contains Tracts. Bundles of axons on the central nervous system
• Allows:
• Two hemispheres to connect and integrate ‘talk’
• Produces the neurotransmitter dopamine.

Question 21

Epithalamus

Answer 21

• Forms the roof of the 3rd ventricle
• Connected to the pineal gland – secretes melatonin, regulate sleep/wake cycle with the hypothalamus.
• Provides connections with the limbic system ‘emotions and feelings’.

Question 22

Hypothalamus

Answer 22

• Below the …
• Main ‘visceral’ centre – vital to homeostasis
• Control centre for the autonomic nervous system and endocrine function
• Centre for emotional responses,thermoregulation, water balance and thirst, food intake, sleep/wake cycle

Question 23

Pituitary gland

Answer 23

•Hypothalamus
• secretes hormones that stimulate the pituitary gland to secrete hormones that stimulate other endocrine glands to secrete hormones
Position
• Sits in sella turcica
Pea size and shape
• Attached to hypothalamus
2 major lobes
• Anterior pituitary (adenohypophysis)
• Posterior pituitary (neurohypophysis)

Question 24

Anterior pituitary hormones

Answer 24

Growth hormone - controlled by GHRH & GHIH - stimulates somatic growth, mobilises fats targets muscle, bone, cartilage, liver
FSH - controlled by GnRH - stimulates ovaries to produce oestrogen and stimulates testes to produce sperm
ACTH - controlled by ACRH - stimulates adrenal cortex to produce glucocorticoids
TSH - controlled by TRH - stimulates thyroid glands to release its hormones
Luteinising hormone - controlled by GnRH - stimulates ovaries to produce oestrogen and stimulates testes to produce testosterone
Prolactin - controlled by PRH and PIH - targets breast and stimulates lactation
MSH - stimulates melanocytes to produce melanin, is a CNS NT involved in controlled of appetite

Question 25

Posterior pituitary hormones

Answer 25

Oxytocin - stimulated by hypothalamus in response to cervical and uterine stretching - stimulates uterus to contract/initiates labour, stimulates milk ejection ADH - stimulated by hypothalamus in response to reduced blood volume - stimulates cells in kidneys to reabsorb more water

Question 26

Brain stem

Answer 26

• Contains Midbrain, Pons varioli, and medulla oblongata • Provides a pathway between the spinal cord and the cerebrum • Contains 10 of 12 pairs of cranial nerves • Essential for regulation of physiology essential for life

Question 27

Mid brain and pons

Answer 27

• Mid Brain: Relays auditory and visual information • Pons: Relays sensory information between the cerebrum and cerebellum. Very important in regulating the rhythm of breathing

Question 28

Medulla

Answer 28

• Medulla: blends into the spinal cord • Contains essential motor nuclei such as: • Cardiovascular centre, respiratory centres and Reflex centres of vomiting, coughing, sneezing and swallowing. • Under influence of the hypothalamus • Broadens out to form two pyramids ‘cones’ formed by the cortico-spinal tracts that descend from the motor cortex

Question 29

Cerebellum

Answer 29

• Beneath and protruding under the cerebrum • Processes input from the cerebral motor cortex, brain stem and peripheral sensory receptors. • Provides spatial awareness, balance, precise timing and subconscious regulation of muscular movement (>600 named skeletal muscles)

Question 30

Spinal cordi

Answer 30

• Continuous with the medulla oblongata superiorly • It is covered by meninges and bathed in CSF. • Is larger in the cervical and lumbar regions. • cervical enlargement (superiorly) supplies nerves to and from the upper limbs. • lumbar enlargement (inferiorly) supplies nerves to and from the lower limbs. • The cord typically extends down to the intervertebral disc between the 1st and 2nd lumbar vertebrae. • Conus medullaris – narrowing below lumbar enlargement • Cauda equina - below the conus medularis spinal nerves descent inferior to exit lower intervertebral foramina and have the appearance of a horses tail. • The meninges extend down to 2nd sacral vertebra • Filum terminale arises from the conus medularis

Question 31

Spinal cord injury

Answer 31

• C3 and above: loss of diaphragm function – requires artificial ventilation • C4 significant loss of use of biceps and shoulders • C5 also loss of use of wrists and hands • C6 limited wrist control, loss of hand control • C7 and T1 some use if arms but limited, tends to represent a threshold for independent living • T1-T8 intercostal and abdominal muscles affected • Lumbar region effects on hips and legs

Question 32

Pathology of the CNS

Answer 32

Vascular • Stroke • Subarachnoid, subdural, extradural haemorrhage Infections • Meningitis • encephalitis Structural disorders • Brain or spinal cord injury • Brain or spinal cord tumours Seizure disorders • Epilepsy Degeneration • Parkinson's • Alzheimer's Autoimmune / inflammatory • Multiple sclerosis • Bells palsy Mental health disorders • Schizophrenia • Depression

Question 33

Subarachnoid haemorrhage

Answer 33

Description • Intracranial haemorrhage with blood in the subarachnoid space. Causes • Risk factors include family history, hypertension, heavy alcohol consumption, connective tissue disorders, trauma, due to an aneurysm or AVM Symptoms • Worst headache ever. • Photophobia Diagnosis • CT – generally done first. • MRI – more sensitive and can look for causes • Angiography – gold standard for diagnosis of vascular abnormalities Complications • Increased intracranial pressure – may require shunt / drain • Patients can develop neurogenic pulmonary oedema • Can result in PEA (pulseless electronic activity) Treatment • Depends on cause

Question 34

Subdural haemorrhage

Answer 34

Description • Blood within the subdural space between the dura and the arachnoid • Generally look crescent shaped. Causes • Mainly trauma Symptoms • Unconscious or decreased conscious level • Abnormal pupil reaction to light. Diagnosis • Unilateral in adults, often bilateral in children • CT – homogenous, hyper dense collection • MRI – most sensitive standard sequence if FLAIR Complications • Can be chronic in older patients Treatment • Depends on size and effect on surrounding brain • May watch and wait • If large will surgically evacuate

Question 35

Extradural haemorrhage

Answer 35

Description • Acute haemorrhage between the dura mater and the skull • Increases intracranial pressure Causes • Skull trauma, most commonly with a fracture Symptoms • History of head trauma with decreasing consciousness, nausea, pain Diagnosis • CT head is the gold standard – ‘lemon shaped’ mass. May also see midline shift and brainstem herniation. • MRI – not used acutely but may be useful for assessing contusions Complications • Infection • Cerebral ischaemia • Seizures Treatment • Conservative • Surgery

Question 36

Meningitis

Answer 36

Description • Infection of the meninges Causes • Bacterial or viral infection Symptoms • Stiff neck, fever, headache, vomiting Diagnosis • CSF analysis is required to confirm cause and plan treatment (spinal tap) • CT is often performed pre spinal tap to assess for increased intracranial pressure or brain herniation / bleed • MRI with contrast can demonstrate abnormal meningeal enhancement (seen in up to 50%). Can also exclude other causes Complications • Seizures, long term disabilities, meningococcal meningitis can lead to loss of extremities Treatment • Antibiotics

Question 37

Spinal cord tumours

Answer 37

Description • Rare, many different types. • Schwannoma – benign tumour of schwann cells – most common tumour of the peripheral nerves Causes • Generally solitary and random • May be linked to patients with neurofibromatosis type 2 Symptoms • Local pain and nerve dysfunction Diagnosis • MRI is the best imaging method. If in acute pain patients may have a CT • Will see a well defined mass, may have a fatty appearance • Rarely calcify Complications • Slow growing • Very rarely undergo malignant change Treatment • Surgery

Question 38

Brain tumours

Answer 38

Glial tumours = astrocytoma and oligodendroglioma Non-glial = meningioma, schwannoma pituitary pineal lymphoma Mestates = lung breast melanoma renal and colon

Question 39

Alzheimer’s

Answer 39

Description • Neurodegenerative disease (60-80% of all dementias) • Thought to be due to amyloid plaques which form in the brain and stop the neuron’s functioning correctly along with decreased production o acetylcholine Causes • risk factors include age, female gender, hypertension Symptoms • Memory deficits Diagnosis • Generally done by clinical examination. • CSF to exclude other causes • CT can show cortical atrophy but not detailed • MRI demonstrated atrophy better • SPECT / PET – can help give a prognosis of decline Complications • Progressive decline Treatment • There are many drugs to slow or delay progress but no definitive cure

Question 40

MS

Answer 40

Description • Demyelinating disorder. • There is destruction of normally myelinated structures • Patients develop lesions in different areas of the brain and at different times Causes • May be an infective link Symptoms • depends on plaque location Diagnosis • Generally clinical history, oligoclonal bands in the CSF and MRI findings • CT – non specific and may look normal • MRI – good for diagnosis and follow up to assess disease progression • T1 – black holes (hypointense lesions) Complications • Disease progression Treatment • Prognosis varies widely from patient to patient • Medicines aim to stop progression