20. Pathology of the Central Nervous System- 1 Flashcards Preview

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1

Functions of the nervous system

Basic : Sensory → Motor
(mediated by central and peripheral nervous system, autonomic and somatic)

Higher :
Consciousness
Complex and learned motor skills
Memory and planning
Communication/language etc…

2

Brain

Cerebral hemispheres
Grey matter
White matter
Basal ganglia
Ventricular system
Brain stem
Cerebellum

3

Meninges

Membranous coverings of the central nervous system
Protective function and important in production of cerebrospinal fluid

4

Blood vessels - Arteries

The cerebral arteries supply a defined territory within the cerebral cortex

If blood supply to a particular part of the brain is interrupted, the patient will develop symptoms due to lack of function of the part of the brain supplied by that vessel

5

The skull

The skull is a bony box which cannot expand
If the volume of tissue or fluid inside the skull increases the intracranial pressure rises
This results in herniation where a part of the brain moves from one compartment of the skull to another

6

Herniation

Brain herniation frequently presents with abnormal posturing[2] a characteristic positioning of the limbs indicative of severe brain damage. These patients have a lowered level of consciousness, with Glasgow Coma Scores of three to five.[2] One or both pupils may be dilated and fail to constrict in response to light.[2] Vomiting can also occur due to compression of the vomiting center in the medulla oblongata.

7

Spinal Cord

Communication of motor and sensory functions between brain and peripheral nervous system

8

Basic Neuroanatomy

Spinal and cranial nerves
Branches of above linking CNS to peripheral sensory receptors and effector organs (muscles & glands)
Autonomic and somatic nervous systems

9

Cells…

Neurons - the processors
Glial cells - supporting functions
- Schwann cells astrocytes & oligodendrocytes

10

Localisation of motor and sensory territories

Post-central Gyrus = Sensory cortex
Pre-central gyrus = Motor cortex

11

Speech and language

Broca’s area - Frontal lobe, anterior to pre-motor cortex
- Predominantly responsible for speech
production
Wernicke’s area - Temporal lobe, posterior to auditory
cortex
- Speech processing and comprehension
of written and spoken language

12

Basic functional anatomy of the CNS

Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
Brain stem
Cerebellum

13

Frontal lobe

Complex executive functions involved in decision making; Emotional reactions: Formation of some types of memory; Motor cortex; Olfactory function; Generation of fluent speech

14

Parietal lobe

Sensory cortex and processing of sensory information

15

Temporal lobe

Language functions including auditory cortex and comprehension of written and spoken words; Memory

16

Occipital lobe

Visual cortex

17

Brain stem

Conduction of major motor and sensory pathways; Control of cardiorespiratory function and consciousness; Cranial nerve roots

18

Cerebellum

Precise motor control; ?Others – language, attention (not yet well defined)

19

Basic functional anatomy of the CNS

Spinal cord nerve roots:
Specific spinal nerves innervate defined motor functions and sensory territories
Damage to spinal cord at a specific level will cause loss of function of spinal nerves below that level
Sensory
Dermatomes:

20

General and focal abnormal neurology

Focal neurological signs:
a set of symptoms or signs in which causation can be localized to an anatomic site in the central nervous system

Generalised neurological abnormality:
Essentially an alteration in level of consciousness

21

Clinical application (1)

People who have regular contact with patients are often more likely to notice subtle changes in neurological parameters allowing prompt investigation and treatment
Basic neurological examination often allows localisation of lesion/injury in a patient with focal neurology

22

Clinical application (2)

Imaging is usually required to confirm and better characterise the nature of the pathological process
Identification of the likely site by examination can assist in the precise radiological identification of a lesion
Assessment of consciousness allows identification of progression of a neurological insult

23

Examples of focal neurological signs
Frontal lobe

Anosmia
Inappropriate emotions
Expressive dysphasia
Motor impairment

24

Examples of focal neurological signs
Parietal lobe

Receptive dysphasia
Sensory impairment

25

Examples of focal neurological signs
Temporal lobe

Cortical deafness
Receptive dysphasia

26

Spinal cord lesions

Physical examination helps to identify the level of injury in spinal cord lesions
Signs limited to a single dermatome or nerve root suggest either a focal nerve root injury or injury to a peripheral nerve
Signs affecting several nerve roots below a certain level eg. Complete paralysis of body and legs with maintained head and neck movement is caused by injuries to the cervical spine (usually traumatic)

27

Diffuse neurological injury

Usually manifest as impairment of consciousness
Most often due to  intracranial pressure (ICP)
May occur as a primary process or as a secondary to response to a focal injury

28

Causes of reduced consciousness

May be obvious on external examination (eg. Trauma) or easily identified on basic observations (eg. Hypoxia, hypothermia)
May require additional bedside tests or more clinical history (eg. Hypo/ hyperglycaemia, post-ictal state in an epileptic patient)

29

Assessing consciousness

Basic:
Assess responsiveness
A : Alert
V : Voice
P : Pain
U : Unresponsive

30

Assessing consciousness

Things can change very quickly

You may be the first person to become aware of a reduction in conscious level

Prompt action is essential