Slide 1 - Definition of Dementia Dementia refers to an acquired persistent loss of intellectual functions due to a brain disorder. This is not a normal part of the aging process, even though the vast majority of persons who experience a dementia are persons age 65 or older. Dementia is really a broad, umbrella term. A medical diagnosis is required to determine the underlying cause or causes of symptoms. In the past, terms like “senility” and “hardening of the arteries” were commonly used to describe dementia but do not accurately explain the disease processes at work.
Nervous system: introduction 2 INVESTIGATION OF NEUROLOGICAL DISEASES:
It is often possible to detect 'epileptiform' abnormalities in between seizures in the form of 'spikes' & 'sharp waves' that support a clinical diagnosis , enhanced by hyperventilation, photic flicker, sleep & some drugs.
During an epileptic seizure, high-voltage disturbances can be recorded, may be generalised, as in the 3 cycle/s 'spike & wave' of childhood absence epilepsy (petit mal), or more focal, as in partial epilepsies.
It is unusual to record a seizure itself, except in the case of childhood absence epilepsy.
EEG data from 100-1000 repeated stimuli are averaged electronically, noise is removed & an evoked potential recorded & its latency (the time interval between stimulus onset & the maximum positive value of the evoked potential, P100) &litude can be measured.
Can be measured following visual, auditory or somatosensory.
Visual evoked potentials(VER), most commonly used.
Abnormalities of the evoked potential indicate damage to the relevant pathway, either in the form of a conduction delay (increased latency) or reduced amplitude, or both.
With MRI, evoked potentials is restricted to specialised indications, as a semi-objective measure of visual function.
By measuring the response latency to stimulation of a nerve at two different points along its length, it is possible to calculate nerve conduction velocities (NCVs), for both sensory & motor nerves; typical values are 50-60 m/s.
Slowing of conduction velocity is suggestive of peripheral nerve demyelination & may be either diffuse (as in a demyelinating peripheral neuropathy) or focal (as in pressure palsies or conduction block).
TECHNIQUES AVAILABLE FOR IMAGING THE NERVOUS SYSTEM
Plain X-rays only used for showing fractures or foreign bodies CT is investigation of choice for stroke Intra-arterial X-ray contrast angiography still 'gold standard' Ionising radiation Reactions to contrast Myelography & angiography are invasive & carry risk Widely available Relatively cheap Relatively quick Plain X-rays CT Radiculography Myelography Angiography radio-opaque tissues /substances (bone, calcium, metal, iodinated contrast) X-ray Comments Disadvantages Advantages Applications Principle Technique
Increasing application Functional MR / spectroscopy. Expensive Less widely available MRA looks at blood flow not vessel anatomy claustrophobic Pacemakers C/I. High-quality soft tissue imaging Good views of posterior fossa /temporal lobes No ionising radiation Non-invasive Structural imaging MRA Functional MRI MR spectroscopy depends on free hydrogen/water content; signals changed by movement (e.g. flowing blood) MRI
Useful as screening tool Increasingly used as basis for carotid endarterectomy Operator-dependent Poor anatomical definition Cheap Quick Non-invasive Doppler Duplex scans Echoes from high- frequency sound source localise structure; Doppler principle usedto measure flow rate U/S
Isotope scans now obsolete SPECT &PET used increasingly in management of epilepsy/ dementia Poor spatial resolution Ionising radiation Expensive (especially PET) Not widely available In vivo imaging of functional anatomy (e.g. ligand binding, blood flow) Isotope brain scan SPECT PET Radio-labelled isotopes Radio- isotope
CSF PARAMETERS IN HEALTH & SOME COMMON DISORDERS
Glucose Glucose Often +ve. Can be positive Can be positive Can be positive Negative Negative Oligoclonal bands Sterile ZN or TB culture positive Sterile/virus detected Organisms on Gram stain &/or culture Sterile Sterile Microbiology N/increased Increased Normal/increased Increased Increased < 0.45 g/l Protein Normal Decreased Normal Decreased N > 60% of blood level 0-50 lymphocytes 50-5000 lymphocytes 10-2000 lymphocytes 1000-5000 polymorphs N/slightly raised 0-4 *10 6 /l White cell count Normal Normal Normal Normal Raised 0-4 *10 6 /l Red cell count Clear Clear/cloudy Clear Cloudy Bloody/ Xanthochromic Clear Colour Normal N/increased Normal N/increased Increased 50-180 mm of water Pressure Multiple sclerosis Tuberculous meningitis Viral meningitis Acute bacterial meningitis Subarachnoid haemorrhage Normal