FYS 4250 Lecture 6

Case 6 - Paramedics are sent for the international terminal of the airport, to a 30 year-old male in a full tonic-clonic seizure.

Case 6 http://graphics8.nytimes.com/images/2007/08/01/health/adam/19076.jpg - His medical history is unknown, but the first thing is to protect him from injury and make sure his airways are open. 10 mg of diazepam is administered, but the patient continues to seize until his arrival to the ED.

Case 6

Case 6 Patients vital signs at arrival: Blood pressure 220/117 mmHg, heart rate 128 beats per minute, respiratory rate 22 breaths per minute, oxygen saturation of 100%, temperature 38.2°C. The examination shows that he has blood-tinged sputum around his mouth and his teeth are clenched. He is tachycardic with normal heart sounds, benign abdomen and normal lungs. ECG reveals a sinus tachycardia with no acute ST changes, a CT-caput, chest X-ray and lumbar puncture are all within normal range. What is the most likely diagnosis?

Case 6 When the doctors find his medical record, there is no sign of previous episodes of epilepsy, or any medical history at all. Still he has all the typical signs of a status epilepticus seizure. The strong hypertension is surprising as a tonic-clonic seizure typically results in a mild hypertension. Their main focus is to manage the ABC (Airways, Breathing, Circulation), and the use of benzodiazepines and antiepileptic agents in order to control the seizures and hypertension. Oxygen is given, and the vital signs are assessed. What is your next step?

Typical EEG electrodes Surprisingly little damage when using needle electrodes. Scalp Cortical Depth http://www.downstate.edu/epilepsy/images/brain-electrodes.jpg http://www.geisinger.kramesonline.com/HealthSheets/168050.img http://www.uwhealth.org/images/ewebeditpro2/upload/5334_Figure_2.jpg

Cerebrum The CNS consists og the spinal cord and the brain lying within the skull. The brain is protected by three membranes and consists of three main parts, Cerebrum, Cerebellum and the brainstem. Both brain and spinal cord are bathed in an extracellular fluid called Cerebrospinal fluid. The brainstem is a connecting bridge between the cerebral cortex, spinal cord and cerebellum, it is centre of several vital functions like controlling the blood pressure and ventilation, and an integration centre for various motor reflexes

EEG Thalamus is a major relay station and an integration centre of all sensory systems. Hypothalamus integrates functions of the autonomic nerve system and Is a hormone controlling centre, cerebellum is a coordinator in the volyntary muscle system, cerebrum is the main part housing the conscious functions of the nervous system The surface layer of the hemisphere is called the cortex

Neuron (Nerve cell) The architecture is not uniform from one part of the brain to another http://paleozonenutrition.com/wp-content/uploads/2012/02/nerve-cell.jpg

Signalpaths in cortex Functional part of the cerebrum is the cerebral cortex (bark, outer, covering). (1.5 to 4.0 mm in thickness) Cell bodies and fiber bundles in a complex architecture 2 types of neurons, pyramidal and nonpyramidal. Nonpyramidal is small, dendrites spring in all directions and contribute none to the surface records Variations in dipole orientation (Dendrite, cell), strength and direction, produce wavelike fluctuations in the recorded potential on the surface

Biopotentail amplifiers

Fysisk institutt - Rikshospitalet EEG waves 1 Alpha 8-13 Hz, awake, quiet relaxed 20-200 uV. Disappear during sleep Beta 14-30 Hz up to 50 Hz if intense mental activity. Beta 1 and beta 2. Affected by mental activity Beta 2 appear during intense activation of the CNS and during tension Theta 4-7 Hz children, and emotional stress among some adults (disappointment and frustration) Delta below 3.5 Hz, sometimes only every 2 or 3 second, deep sleep, infancy and serious organic brain diseases FYS4250 Fysisk institutt - Rikshospitalet 13

Fysisk institutt - Rikshospitalet EEG waves 2 FYS4250 Fysisk institutt - Rikshospitalet 14

Sleep EEG

EEG electrodes Recorded potentials represent a superposition of the field potentials produced by a variety of active neuronal current generators within the volume conductor medium. Complex interconnections

EEG-signals What does this tell about our patient? http://www.fracp.bigpondhosting.com/images/EEG_tonic_clonic_seizure.jpg What does this tell about our patient?

Case 6 After controlling the tonic-clonic seizure, the doctors wonders what might be the source of the epileptic activity. Additional EEG’s after the seizures are all negative, and no abnormalities can be found CT scan, nor are there any findings from the MRI-scan. In order to explore possible neurological diseases, they decide to measure the neural velocity

Membrane potential Nernst equation for potassium K (Nor - Kalium): across a cell membrane with active channels pumping K ions into the cell.

Action potential, excitable cell an adequate stimulus depolarizes the cell membrane so that the treshold level is exceeded, triggering an action potential. Constant speed along the membrane, polarised membrane. Depolarizing of the cell membrane will increase the Na transport into the cell, which will yield a further depolarization and even more Na transport into the cell

Dipoles in the axon Signal propagation relatively small compared to the fiber length. Myelinated nerve cell is about 20 times faster potential propagation. When an action potential is produced, there is no ability to respond to a second stimulus (absolute refractory period) Relative refractory period, action potential can be elicited by an intense supertreshold stimulus. A nerve axon with an absolute refractory period of 1 ms has upper limit of 1000 repetitive discharges per second. Reversal of polarity in the active region because of depolarization, membrane behind is repolarized. No attenuation. Vertebrate neurons are myeliniated, insulated by a sheath of myelin. (Lipoprotein complex. Interupted at regular intervals, -> action potentials are not uniformly distributed along the membrane-> reduce leakage current, decrease membrane capacitance and improves transmission properties, esp. Speed. Incidence of multiple scleroris (MS) disintegration om myelinated layer, is increased by 0.7% for each latitude northwards

Summing up in the nerve-cell Both motorical and sensorical fibers are excited simultaneously by electrical stimulus. Dorsal root is sensoric Ventral root is motoric, dorsal root is nervous Stimulation of the many large diametric motoric fibers will give the largest extracellular response. Stimulation of sensoric fibers will excite two groups of sensoric fibres.

Axon in invertebrate animals Resting membrane is slightly permeable to Na+, freely permeable to K+ and CL-. Sodium (virvelløse dyr)

muscle-fibre or axon

Muscle control Reflex arc Sense organ Sensory nerve, sending information CNS, integratorstation. Evaluated -> Motoric decision can be implemented Motor nerve, communicating with peripheral muscle Effector organ, like skeletal muscle fibers. Spindle er lengdereseptorer

Neural velocity Nerve stimulation at two different sites, subtraction of the shorter latency from the longer latency gives conduction time

Neurography The potential is transferred through the median nerve, which is the same size and diameter all the way through the arm. The difference is due to the size of the volume conductor at each location and the radial distance of the measurement point from the neural source. NB Sensory nerve, not motoric nerve

Neurography Simultaneous recordings of compound muscle action potentials (CMAP) from the thenar eminence, and sensory nerve action potentials (SNAP) from the index and middle fingers after stimulation of the median nerve at palm, wrist, elbow and axilla. Progressively more proximal series of stimuli elicited nearly the same CMAP. Linear reduction in SNAP from the wrist to the axilla indicate that this is a physiologic rather than pathologic alteration http://ars.els-cdn.com/content/image/1-s2.0-S001346949800025X-gr2.gif

H-reflex When a mixed peripheral nerve is stimulated with low intensity, only fibers with big diameter will be stimulated because they have the lowest treshold = sensoric fibers. (Spinal reflex). When stimulus is increasing, smaller motor fibers in the mixed nerve are stimulated in addition to the sensory fibers, short latency motoric contraction is produced. (M-wave). Even stronger stimuli, production of H-wave is interfered due to the refraction period of the motor fibers After 5 days in space, this effect diminishes -> reduced excitability in the spinal chord

Reflex

EMG Cross sectional view of the spinal cord. A method for distinguishing between myopathic and neurogenic muscle weakness and wasting

EMG setup http://www.adinstruments.com/sites/default/files/images/rcexp_SEMG-example.jpg

EMG Abnormal spontaneous activity. (A) Fibrillations (*) and positive sharp waves (**) in an acutely denervated hand muscle. (B) Single, doublet, triplet, and multiplet motor unit neuromyotonic discharges. Bursts of discharge are irregular in frequency and the intra-burst frequency of discharge is up to 200 Hz. (C) Fasciculations in the tongue in a patient with amyotrophic lateral sclerosis. The single discharges are irregular and occur on a background of ongoing EMG activity caused by poor relaxation. (D) Myotonic discharges in a patient with dystrophia myotonica. There is a characteristic waxing and waning in frequency (http://jnnp.bmj.com/content/76/suppl_2/ii32/F1.medium.gif) http://jnnp.bmj.com/content/76/suppl_2/ii32/F1.large.jpg Abnormal spontaneous activity. (A) Fibrillations (*) and positive sharp waves (**) in an acutely denervated hand muscle. (B) Single, doublet, triplet, and multiplet motor unit neuromyotonic discharges. Bursts of discharge are irregular in frequency and the intra-burst frequency of discharge is up to 200 Hz. (C) Fasciculations in the tongue in a patient with amyotrophic lateral sclerosis. The single discharges are irregular and occur on a background of ongoing EMG activity caused by poor relaxation. (D) Myotonic discharges in a patient with dystrophia myotonica. There is a characteristic waxing and waning in frequency

EMG SMU = Single motor unit

ERG Electroretinogram Eye 24 mm in diameter. Light transmitting parts -> cornea, anterior chamber, lens and vitreous chamber A transparent fluid is found in the anterior chamber, vitreous chamber is filled with a transparent gel Normal pressure 20 – 25 mmHg, necessary for a clear visual image Glaucoma = high pressure condition, injure the retina. Caused by obstruction of flow between blood and fluid 4 types of nerve cells Photoreceptors, bipolar, horizontal, amacrine and ganglion cells

ERG http://webvision.med.utah.edu/gifswv/DONFig3.gif

ERG A - Early receptor potensial ERP + late receptor potensial LRP B- Bipolare og ganglion celler i innerste lag av retina C – pigment epitel-celler D- av-respond til retina Early receptor potential (ERP) light-induced changes in photopigment molecules (first part) Late receptor potential (LRP) output of the photoreceptors (second part) Absence of b wave

ERG congenital stationary night blindness (CSNB) RP = retina pigmentosa http://www.retinalphysician.com/content/archive/2007/April/jpg%5C9FF1.jpg

Case 6 What is your conclusion? All tests are perfectly normal, except for one thing: The Urine toxicology screen is positive for cocaine. What is your conclusion?

Case 6 This patient was trying to smuggle cocaine into the country by swallowing one or more condoms filled with cocaine. One of the condoms cracks, not a big crack, but enough for allowing a significant amount of cocaine to flow into the intestines and into the blood. This led to a status epilepticus caused by the cocaine, and explains the hypertension as cocaine is highly vasoconstrictive, thus increasing the blood pressure dramatically when the body absorbs large amounts of the drug.