21 Pathology of the Central Nervous System- 1 Flashcards
Areas covered in this lecture:
Functions of the nervous system
Basic anatomy and physiology of central nervous system
An overview of manifestations of focal/generalised neurological injury/disease
In the next lecture – Specific neurological diseases and their presentation and management
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…
Brain
Cerebral hemispheres Grey matter White matter Basal ganglia Ventricular system Brain stem Cerebellum
Meninges
Membranous coverings of the central nervous system
Protective function and important in production of cerebrospinal fluid
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
More detail to come in the next lecture
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
Cells…
Neurons - the processors
Glial cells - supporting functions
- Schwann cells astrocytes & oligodendrocytes
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
Basic functional anatomy of the CNS
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
Parietal lobe: Sensory cortex and processing of sensory information
Temporal lobe: Language functions including auditory cortex and comprehension of written and spoken words; Memory
Occipital lobe: Visual cortex
Brain stem: Conduction of major motor and sensory pathways; Control of cardiorespiratory function and consciousness; Cranial nerve roots
Cerebellum: Precise motor control; ?Others – language, attention (not yet well defined)
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
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
Clinical application
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
Clinical application
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
Examples of focal neurological signs
Frontal lobe = Anosmia Inappropriate emotions Expressive dysphasia Motor impairment
Parietal lobe =
Receptive dysphasia
Sensory impairment
Temporal lobe =
Cortical deafness
Receptive dysphasia
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)
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
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)
Assessing consciousness
Basic: Assess responsiveness A : Alert V : Voice P : Pain U : Unresponsive
Assessing consciousness
More complex: Glasgow coma scale (GCS): Best motor response: 6. obeys commands 5. localises to pain 4. withdraws to pain 3. Flexor response to pain 2. Exterior posturing to pain 1. No response to pain
Best verbal response:
- n/a
- Orientated to time, place, person
- Confused conversation
- Inappropriate speech
- Incomprehensible speech
- None
Eye opening:
- n/a
- n/a
- Spontaneous
- Eye opening to speech
- Eye opening response to pain
- No eye opening
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
Summary
Neurological anatomy and function is very complex
Location of injury/pathology determines symptoms
Things can change quickly important to highlight changes to the team
