Cns Intro Davidson Plus2.


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Medical college lectures neurology 5th year.

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  • 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.
  • Cns Intro Davidson Plus2.

    1. 1. Nervous system: introduction 2 INVESTIGATION OF NEUROLOGICAL DISEASES: <ul><li>Dr. Mohammad Shaikhani. </li></ul>
    2. 2. INVESTIGATION OF NEUROLOGICAL DISEASE <ul><li>1.TESTS OF FUNCTION (CLINICAL NEUROPHYSIOLOGY): </li></ul><ul><li>A. EEG. </li></ul><ul><li>B. EPs. </li></ul><ul><li>NCS/EMG. </li></ul><ul><li>2.Imagings. </li></ul><ul><li>3. Special tests: </li></ul><ul><li>A. Blood tests. </li></ul><ul><li>B. CSF testing </li></ul><ul><li>C. Biopsies. </li></ul>
    3. 3. TESTS OF FUNCTION (CLINICAL NEUROPHYSIOLOGY) <ul><li>More restricted application than imagings. </li></ul><ul><li>Essential in certain conditions. </li></ul><ul><li>Include: </li></ul><ul><li>EEG. </li></ul><ul><li>Evoked potentials (EPs). </li></ul><ul><li>Nerve conduction studies/electromyography (NCS/EMG). </li></ul>
    4. 4. EEG: <ul><li>When the eyes are shut, the most obvious frequency over the occipital cortex is 8-13/s( alpha rhythm) disappears when eyes opened. </li></ul><ul><li>Other frequency bands seen over different parts of the brain in different circumstances are beta (faster than 13/s), theta (4-8/s) & delta (slower than 4/s). </li></ul><ul><li>Lower frequencies predominate in the very young & during sleep. </li></ul>
    5. 7. clear right temporal sharp waves in two patients with right temporal lobe epilepsy
    6. 8. 10-second EEGs: Seizure Evolution N Pre During Post
    7. 9. EEG: Indications in CNS diseases: <ul><li>The management of epilepsy (the most important). </li></ul><ul><li>A global increase in fast frequencies (beta) seen with sedating drugs (e.g. benzodiazepines), </li></ul><ul><li>Marked slowing over a structural lesion as a tumour or an infarct, but with modern neuro-imaging, it had lost its use in localizing such lesions. </li></ul><ul><li>Still useful in; </li></ul><ul><li>The management of patients with disturbance of consciousness or sleep. </li></ul><ul><li>The diagnosis of cerebral diseases as encephalitis. </li></ul><ul><li>In certain dementias (e.g. sporadic CJD). </li></ul>
    8. 10. EEG In epilepsy: <ul><li>Only in rare circumstances EEG provide unequivocal evidence of epilepsy </li></ul><ul><li>It is not useful as a diagnostic test for the presence of epilepsy because: </li></ul><ul><li>50% of patients with proven epilepsy will have a normal 'routine' EEG. </li></ul><ul><li>The presence of EEG changes often seen in association with epilepsy does not make a diagnosis (although false +ve rate for clear-cut epileptiform features is < 1/1000). </li></ul><ul><li>Its use is predominantly to: </li></ul><ul><li>Distinguish the type of epilepsy. </li></ul><ul><li>Whether there is an epileptic focus, particularly if surgery for epilepsy is contemplated. </li></ul>
    9. 11. EEG In epilepsy: <ul><li>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. </li></ul><ul><li>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. </li></ul><ul><li>It is unusual to record a seizure itself, except in the case of childhood absence epilepsy. </li></ul>
    10. 12. EEG In epilepsy: <ul><li>Diagnostic value enhance by: </li></ul><ul><li>24 hours tape recorder instead of usual 30-min record. </li></ul><ul><li>Video information to the EEG allows comparison of behaviour with cerebral activity. </li></ul><ul><li>In special circumstances, electrodes can be surgically positioned, e.g. through the foramen ovale, to record from the inferior temporal surface. </li></ul>
    11. 13. Evoked potentials : <ul><li>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) &amplitude can be measured. </li></ul><ul><li>Can be measured following visual, auditory or somatosensory. </li></ul><ul><li>Visual evoked potentials(VER), most commonly used. </li></ul><ul><li>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. </li></ul><ul><li>With MRI, evoked potentials is restricted to specialised indications, as a semi-objective measure of visual function. </li></ul>
    12. 14. Evoked potentials :
    13. 15. Nerve conduction studies & electromyography : <ul><li>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. </li></ul><ul><li>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). </li></ul>
    14. 16. Nerve conduction studies & electromyography : <ul><li>Indications: </li></ul><ul><li>To identify damage to peripheral nerves. </li></ul><ul><li>Whether the pathological process is focal or diffuse </li></ul><ul><li>Whether the damage is principally axonal or demyelinating or in the nerve roots. </li></ul><ul><li>Fine concentric needle electrodes can be inserted into muscle &record fibrillations (a sign of denervation) or myotonic discharges or structural muscle diseases. </li></ul><ul><li>Investigate the NMJ, a decrement is seen in myasthenia gravis. </li></ul><ul><li>Augmentation of the response to repetitive stimulation is seen in the Lambert-Eaton myasthenic syndrome, usually at higher stimulation frequencies. </li></ul>
    15. 17. Imagings: <ul><li>TECHNIQUES AVAILABLE FOR IMAGING THE NERVOUS SYSTEM </li></ul>
    16. 18. 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
    17. 19. 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
    18. 20. 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
    19. 21. 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
    20. 31. Special testes : blood tests <ul><li>Systemic diseases affecting CNS as: </li></ul><ul><li>Confusion due to hypothyroidism(TFTs) </li></ul><ul><li>Stroke due to systemic lupus erythematosus (ANF etc). </li></ul><ul><li>Ataxia due to vitamin B12 deficiency </li></ul><ul><li>Myelopathy due to syphilis(VDRL). </li></ul><ul><li>Haematological tests (e.g. looking for acanthocytes to diagnose neuroacanthocytosis) </li></ul>
    21. 32. Special testes : blood tests <ul><li>Biochemical tests (e.g. creatine kinase in muscle diseases) </li></ul><ul><li>Copper studies in Wilson's disease). </li></ul><ul><li>tests to diagnose infections of the nervous system. </li></ul>
    22. 33. Special testes : blood tests <ul><li>A number of specific antibodies to: </li></ul><ul><li>Acetylcholine receptors &muscle-specific tyrosine kinase (MuSK), in myasthenia gravis </li></ul><ul><li>Voltage-gated calcium channels in Lambert-Eaton myasthenic syndrome. </li></ul><ul><li>Different gangliosides in various types of neuropathy including multifocal motor neuronopathy& Guillain-Barré syndrome (sp Miller-Fisher variant). </li></ul><ul><li>Antineuronal antibodies as a markers of paraneoplastic cerebellar or neuropathic syndromes. </li></ul><ul><li>Basal ganglia neurons found in Sydenham's chorea & encephalitis lethargica. </li></ul>
    23. 34. Special testes : blood tests <ul><li>DNA analysis: </li></ul><ul><li>For diseases caused by increased numbers of trinucleotide repeats, as Huntington's disease, myotonia dystrophy& some types of spinocerebellar ataxia. </li></ul><ul><li>Defects of mitochondrial DNA detected in many conditions as Leber's hereditary optic neuropathy& some syndromes causing epilepsy or stroke-like syndromes. </li></ul>
    24. 35. Special testes : LP <ul><li>Lumbar puncture is indicated in: </li></ul><ul><li>CNS infections (e.g. meningitis or encephalitis) </li></ul><ul><li>Subarachnoid haemorrhage. </li></ul><ul><li>Inflammatory conditions (e.g. multiple sclerosis, sarcoidosis, cerebral lupus) </li></ul><ul><li>Neurological malignancies (e.g. carcinomatous meningitis, lymphoma , leukaemia), </li></ul><ul><li>Measure CSF pressure (e.g. in idiopathic intracranial hypertension) </li></ul><ul><li>Myelography. </li></ul><ul><li>Therapeutic procedures, either to lower CSF pressure or to administer drugs as Methotrexate in ALL. </li></ul>
    25. 36. Special testes : CSF testing <ul><li>CSF is normally clear & colourless. </li></ul><ul><li>Tests include: </li></ul><ul><li>Centrifuging to determine the colour of the supernatant (yellow, or xanthochromic, some hours after subarachnoid haemorrhage) </li></ul><ul><li>Biochemistry (glucose, total protein, protein electrophoresis to detect oligoclonal bands). </li></ul><ul><li>Microbiology (e.g. PCR for herpes simplex or TB), </li></ul><ul><li>Immunology (e.g. paraneoplastic antibodies). </li></ul><ul><li>Cytology (to detect malignant cells). </li></ul>
    26. 37. Special testes : risks of spinal tap. <ul><li>If there is a SOL in the head, LP can result in a potentially fatal shift of intracerebral contents downwards, towards &into the spinal canal (coning). </li></ul><ul><li>LP is contraindicated until imaging head (by CT or MRI) has excluded a SOL or hydrocephalus, if there is: </li></ul><ul><li>Any suggestion of raised intracranial pressure (e.g. papilloedema), </li></ul><ul><li>Depressed level of consciousness. </li></ul><ul><li>Focal neurological signs suggesting a cerebral lesion. </li></ul><ul><li>The patient is likely to bleed, as in thrombocytopenia, DIC or warfarin therapy, unless specific measures are taken to compensate for the clotting deficit on a temporary basis. </li></ul><ul><li>LP is not contraindicated in those on aspirin. </li></ul>
    27. 38. Special testes : spinal tap side effects. <ul><li>30% followed by low-pressure headache, which can be severe. </li></ul><ul><li>Transient radicular pain during the procedure,pain over the lumbar region. </li></ul><ul><li>Infections as meningitis extremely rare if sterile procedures followed. </li></ul>Needle between L3,4 or L4,5
    29. 41. 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  
    30. 42. Xanthochromic CSF in SAH:
    31. 43. Biopsies : Nerve. <ul><li>Nerve biopsy at the ankle or radial nerve at the wrist, for histopathology, useful for; </li></ul><ul><li>Identify underlying causes in demyelinating neuropathies (e.g. vasculitic) or, occasionally, infiltration with abnormal substances as amyloid. </li></ul><ul><li>It is not performed unless it is reasonably likely to diagnose a potentially treatable condition as an inflammatory neuropathy, as there is an appreciable morbidity. </li></ul>
    32. 44. Biopsies : Muscle. <ul><li>Often quadriceps. </li></ul><ul><li>Indications include the investigation of primary muscle disease, to distinguish neurogenic wasting, for myositis or myopathy. </li></ul><ul><li>Histology /enzyme histochemistry can also be helpful in the diagnosis of more widespread metabolic disorders, as mitochondrial &some storage diseases. </li></ul><ul><li>Pain & infection can follow, much less than after nerve biopsy. </li></ul>
    33. 45. Biopsies : Brain. <ul><li>In situations in which the nature of lesions is not clear,as in unexplained degenerative diseases (e.g. unusual dementias) to diagnose potentially treatable disease. </li></ul><ul><li>Brain biopsy stereotactically through a burrhole in the skull, complication much lower than open craniotomy, but haemorrhage, infection& death still occur. </li></ul><ul><li>Brain biopsy is only considered if a diagnosis cannot be reached in any other way. </li></ul>
    34. 46. Signs of motor neuron lesions : <ul><li>Lower motor neuron lesions: as in poliomyelitis. </li></ul><ul><li>A. Flaccid weakness. </li></ul><ul><li>B. Low tone. </li></ul><ul><li>C. Absent reflexes. </li></ul><ul><li>D. Babenski: equivocal. </li></ul><ul><li>C. preserved superficial reflexes as abdominal reflex. </li></ul><ul><li>Upper motor neuron lesions: as in CVA & Brain tumors. </li></ul><ul><li>A. Spastic paralysis. </li></ul><ul><li>B. High muscle tone (spastic). </li></ul><ul><li>C. Exadurated reflexes. </li></ul><ul><li>D. absent superficial reflexes as abdominal reflex. </li></ul><ul><li>C. Dorsiflexed (upgoing) Babenski reflex. </li></ul>
    35. 47. Spasticity vs rigidity : both increase muscle tone <ul><li>Spasticity: in upper motor neuron lesions. </li></ul><ul><li>Of clasp-knife character. </li></ul><ul><li>Rigidity: in parkinsonism, of 2 types. </li></ul><ul><li>A. Lead pipe: increase tone throughout ranges of movements, when rigidity predominates over tremor. </li></ul><ul><li>B. Cog-wheel: increase tome intermittent, when tremor predominates. </li></ul>