Monday, January 7, 2008

6 - forensic medicine mcqs - 31 to 35

31. Contre-coup injuries are seen in:
1. Brain.
2. Heart.
3. Liver.
4. Pancreas.
1. Brain.
The Essentials of Forensic Medicine and Toxicology 21st Edition : K.S.Narayana Reddy Page
When a static head is struck, there is usually a similar lesion overt the part of the brain of the area. But when the head being in motion, strikes a static or relatively static object, then there will be a Coup (blow, impact) coup lesion at a site diagonally opposite to the site of the impact or the coup injury.
Self Explanatory
Contre Coup is not common in Occipital Region : A coup lesion on the Frontal region produces a contre - coup lesion in the temporal lobe of the brain.
The contre coup lesion may in over
o the vessels à haemorrhage
o the brain matter à Contusion
IF the force is not perpendicular, then the contre-coup lesion may be due to the shearing force
Note that there is another Contre - Coup : The Contre-copuy Fracture:
When the impact is over the occipital region, the force will be directed anteriorly. In the course of its path, the force causes vibration. Where ever the force passes through a thin and weak bone in its path, it may cause fracture of that bone. Thus in the case of reasonably heavy impact on the occipital bone, there may not be any fracture at the site of impact due to toughness of the occipital bone, but the force, when passes anteriorly causes fracture of the thin orbital plates of the frontal bone. Mechanisms of contre-coup injury to brain is, however, totally different.

32. Hydrogen peroxide is used in all the following chemical tests for blood except
1. Benzedine test.
2. Phenophthalein test.
3. Orthotoluidine test.
4. Teichmann's test.
4. Teichmann's test.
The Essentials of Forensic Medicine and Toxicology 21st Edition : K.S.Narayana Reddy Page 381 to 382
Principles of Forensice Medicine 1st Edition : Apoorva Nandy : Pages 115 to 117
All the tests use Hydrogen peroxide (H2O2)
1. Benzedine test: Stain Extract in Test Tube + few drops of 10 % Benzidine in Glacial Acetic Acid + few drops of H2O2 à Blue Colour indicates Positive test (Similarly the stain is moistened with Normal Saline and a blotter is pressed over the area + Benzidine Solution + H2O2 à Blue Colour indicates Positive test.
2. Phenophthalein test (Kastle mayer test): Diluted Stain Extract + Reduces Alkaline Phenopthaline + few drops of H2O2 à Pink Colour indicates Positive test
3. Orthotoluidine test (Kohn and O’Kelly test): Equal volume of Working Solution (4% Orthotoludine in Ethyl Alcohol + Glacial Acetic Acid + Distilled Water in equal amounts ) and H2O2 are mixed . Then few drops of this mixture is added to the stain extract in a test tube à Blue or Green Colour indicates Positive test
4. Teichmann's test (Haemin crystal test): NaCl + 2 to 3 drops of Galcial Acetic Acid is palced on the stain on a glass slide. Coverslip applied + Evaporated by heating over small flame. Examined under Microscpe. Faint yellowish-red to brownish black rhombic crystals of heamin or haematic chloride arranged single or in clusters are seen if blood is present. Bubbles of gas are given with Addition of a drop of Hydrogen peroxide
In the first 3 tests, H2O2 is an essential part in DIAGNOSIS, where as in the Haemin Crystal test, Hydrogen peroxide is used only for CONFIRMATION. So we take that as an answer. Also note that the first 3 tests use the presence of Peroxide (which needs of H2O2) as the basis where as Teichmann test queries for Heme
Leucomalachite Green Test is another test that uses H2O2
Blood can be conveniently detected by Spectroscopic Examination. In fact in this modality we can even find the state of hemogloblin (Oxy or Carboxy etc) based on the absorption bands.
When Carboxy hemoglobin is present in the blood we can tell with confidence that the burns were antemortem (in addition to other findings such soot particles in trachea)
o However note that not all Antemortem burns will have Carbon monoxide. There are few circumstances in which CO may not be found inspite of the burns being antemortem
§ Rapid Death
§ Convection Air Currents
§ Low Production of CO,
§ Flash fire (conflaguration in Chemical Plant)
§ Inhalation of superhated air leading to suffocation
§ Explosion where death is instantaneous

33. Disputed maternity can be solved by using the following tests except:
1. Blood grouping.
2. HLA typing.
3. Preciptin test
4. DNA fingerprinting.
3. Preciptin test
The Essentials of Forensic Medicine and Toxicology 21st Edition : K.S.Narayana Reddy Page 383
Disputed Maternity (as well as paternity) can be found by
Blood Grouping (See chapter of Virginity, Pregnancy and Delivery - Reddy : Affiliation Cases)
HLA Typing and
DNA Finger printing as well as a whole lot of features
Self Explanatory
Preciptin test is used to find albuminous substances from any part of the human body. It is Species specific (not individual specific) and we can’t use this for disputed paternity. !!!!
Preciptin test is an Immunological method : Other Immunological methods include
§ Antiglobulin consumption test
§ Gel Diffusion
§ Double Diffusion in Agar Gel
§ Precipitation Electrophoresis
Isoenzyme methods are also used for species identification. They are more specific and less sensitive than Immunological Method

34. A person was brought by police from the railway platform. He is talking irrelevant. He is having dry mouth with hot skin, dilated pupils, staggering gait and slurred speech. The most possible diagnosis is:
1. Alcohol intoxication.
2. Carbamates poisoning.
3. Organophosphorous poisoning.
4. Datura poisoning.
4. Datura poisoning.
The Essentials of Forensic Medicine and Toxicology 21st Edition : K.S.Narayana Reddy Page 520
Agents that can competitively block the binding of acetylcholine to CNS and parasympathetic postganglionic muscarinic neuroreceptors include
o Antihistamines (H1 blockers),
o Belladonna alkaloids and related agents
§ Atropine, glycopyrrolate, homatropine, hyoscine, ipratropium, scopolamine,
o Drugs for Parkinson's disease
§ Benztropine, biperiden, trihexyphenidyl
o Topical mydriatics
§ Cyclopentolate, tropicamide
o Neuroleptics
§ Clozapine, olanzepine, phenothiazines
o Skeletal muscle relaxants
§ Cyclobenzaprine, orphenadrine
o Smooth-muscle relaxants
§ Clidinium, dicyclomine, isometheptene, oxybutynin
o Tricyclic antidepressants, and
o Plants
§ Datura stramonium, or jimson weed
§ Mushrooms.
Clinical Toxicity
o Within
§ 1 hour of acute overdosage
§ 1 to 3 days in cases of chronic poisoning.
o Toxic doses are only slightly greater than therapeutic ones.
o CNS manifestations
§ Agitation, ataxia, confusion, delirium, hallucinations, and movement disorders (choreoathetoid and picking movements).
§ Lethargy, respiratory depression, and coma may occur.
o Peripheral nervous system findings
§ Decreased or absent bowel sounds,
§ Dilated pupils,
§ Dry skin and mucosal surfaces,
§ Urinary retention,
§ Tachycardia
§ Increased Blood pressure
§ Tachypnea
§ Increased temperature
o Neuromuscular hyperactivity
§ Rhabdomyolysis and
§ Hyperthermia.
o First-generation H1 blockers (diphenhydramine and probably others)
§ Tricyclic antidepressant-like cardiotoxicity and seizures.
o Second-generation antihistamines (astemizole, terfenadine) nonsedating
§ Because of class III antiarrhythmic activity,
§ QT-interval prolongation with subsequent ventricular tachyarrhythmias,
§ especially torsade de pointes,
o Detecting these agents in the urine.
o Confirmed by demonstrating resolution of anticholinergic toxicity in response to physostigmine.
Self Explanatory
Comments : Treatment of AntiCholinergics
Activated charcoal adsorbs these agents effectively and is the preferred method of gastrointestinal decontamination.
Agitation may respond to benzodiazepines, and comatose patients may require intubation and mechanical ventilation.
Cardiovascular toxicity and arrhythmias should be treated as described for antiarrhythmics and tricyclic antidepressants.
Physostigmine, an acetylcholinesterase inhibitor, reverses anticholinergic toxicity.
o It is indicated primarily for uncontrolled agitation and delirium.
o The dose is 1 to 2 mg given intravenously over 2 to 5 min; the dose can be repeated if there is an incomplete response or recurrent toxicity.
o If signs of cholinergic poisoning occur (see "Organophosphate and Carbamate Insecticides," below), they can be reversed by atropine in half the amount of physostigmine given.
o Physostigmine should not be given for seizures or for coma; its arousal effects are nonspecific and cannot be used for diagnostic purposes.
Physostigmine is contraindicated in the presence of cardiac conduction defects or ventricular arrhythmias because it can cause asystole in such patients.
Remember the Mnemonic for Atropine toxicity
o Hot as a Hare
o Blind as a bat
o Dry as a bone
o Red as a beet
o Mad as a Hen
Atropine was first used as a homicidal poison. The name is derived from the senior of three legendary Fates, Atropos, who cuts with shears the web of life spun and woven by her sisters Clotho and Lachesis (There is a synthetic atropine like drug called as Lachesine) The term belladonna (in Italian meaning beautiful (bella) women (donna) refers to the once fashionable female practice of using an atropine extract to dilate the pupils (as a part of make up.)

35. A middle aged man presents with paraesthesia of hands and feet. Examination reveals presence of Mees. lines in the nails :md rain drop pigmentation in the hands. The most likely causative toxin for the above mentioned symptoms is:
1. Lead.
2. Arsenic
3. Thallium.
4. Mercury.
2. Arsenic
The Essentials of Forensic Medicine and Toxicology 21st Edition : K.S.Narayana Reddy Page 462
Arsenic is termed a metalloid as it has properties of both metals and non-metals.
o Trivalent (e.g. arsenic trioxide, arsenious acid, and arsenites) and
o Pentavalent (e.g. arsenic pentoxide, arsenic acid, and arsenates) derivatives.
o Inorganic arsenical compounds may generate arsine gas when in contact with acids and reducing metals (e.g. iron and zinc) or with sodium hydroxide and aluminium.
o Electronics industry,
o Production of special types of crystal and optical glass,
o Hardening lead and copper alloys,
o Manufacture of fireworks,
o Wood preservative and
o Pesticide. It is a byproduct of copper smelting.
In exposed individuals high concentrations of arsenic are present in
o Bone,
o Hair, and
o Nails. The half-life is in the range of 1 to 3 days.
Excretion is predominantly in the
o urine as mono- and dimethyl-derivatives.
Acute poisoning
o This can follow accidental, suicidal, or deliberate ingestion,
o Toxicity being largely dependent on the water solubility of the ingested compound.
§ Within 2 h of substantial ingestion of a soluble arsenical compound, severe haemorrhagic gastritis or gastroenteritis may ensue with collapse and death usually within 4 days.
§ A metallic taste, salivation, muscular cramps, facial oedema, difficulty in swallowing, hepatorenal dysfunction, convulsions, and encephalopthy are reported.
§ A peripheral neuropathy (predominantly sensory), striate leukonychia (Mees' lines) and hyperkeratotic, hyperpigmentated skin lesions are common in those surviving a near fatal ingestion.
§ In moderate or severe arsenic poisoning investigations may show anaemia, leucopenia, thrombocytopenia, and disseminated intravascular coagulation. ECG abnormalities have been reported and include QT prolongation and ventricular arrhythmias.
o Exposure to arsenic trioxide and trichloride dust causes irritation of the eyes, nose, throat, and lower respiratory tract. Corrosive skin damage may follow skin contact with arsenical compounds such as arsenious acid and arsenic trichloride.
Chronic poisoning
o Source
§ Contaminated drinking water or
§ “Tonics” containing inorganic trivalent arsenical compounds
o Features
§ Progressive weakness,
§ Anorexia, Nausea, Vomiting, Stomatitis, Colitis,
§ Increased salivation, Epistaxis, Bleeding gums, Conjunctivitis,
§ Weight loss, and Low grade fever.
§ Hyperkeratosis (palms and soles of the feet)
§ “Raindrop” (skin),
§ “Mees” (nails).
§ Skin cancer (usually squamous cell epithelioma)
§ A symmetrical peripheral neuropathy is typical.
§ Sensory symptoms predominate but motor involvement is also
§ Central nervous system effects
· hearing loss,
· psychological impairment and
· EEG changes.
§ disturbances of liver function
§ Ulceration and perforation of the nasal septum.
Chronic exposure to trivalent and pentavalent forms of arsenic has been linked to excess lung cancer and lung cancer occurring in lead, tin, and copper smelter workers has been attributed to arsenic.
1. Lead poisoning presents with a whole lot of features like Aneamia, Colic, Neuropathy, facial pallor, lead line or Burtonian line, lead encephalopathy , optic atrophy etc.
2. Acute Arsenic Resembles Diarrhoea where as Chronic Arsenic resembles “fading Measles”
3. Thallium poisoning resembles Guillain Barre Syndrome.
4. Minamita disease, hatter’s shakes and mercurial erethesm are a few of the prominent features of Mercury Poisoning.
Dimercaprol (British Anti-Lewisite, BAL) given by deep intramuscular injection (2.5-5 mg/kg four hourly for 2 days followed by 2.5 mg/kg intramuscularly twice daily for 1 to 2 weeks).
DMSA (succimer) and DMPS (unithiol) are more effective in reducing the arsenic content of tissues and, unlike dimercaprol they do not cause accumulation of arsenic in the brain DMSA and DMPS may be given orally (in a dose of 30 mg/kg body weight daily).
The fact that Arsenic is tasteless and odorless was known even eras ago. It is alleged that the governor of St.Helena “slow poisoned” the “petit corporal” while he was in the jail as a prisoner of Britain. But they didn’t perhaps know that Arsenic is a BAD homicidal poison as it can be detected even centuries after in Bone and Hair (as was detected from Napolean’s mortal remains).

1 comment:

Where time stands still..! said...


I did not know that atropine was named after a myth.. interesting!


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