DISORDERS OF CONSCIOUSNESS Unit #3 – Disorders of Consciousness
Disorders of consciousness may occur as episodic phenomena or may be continuous. Included under the rubric of episodic impairment or loss of consciousness are seizures and syncope, while the state of coma involves prolonged unresponsiveness. The principal review for this unit is to be found in Chapters 8 and 10 as well as some parts of Chapter 1 of Clinical Neurology. Extra review material from your Neurosciences syllabus includes lectures 42a and 43 on Consciousness and Coma. A. Learning Objectives
At the end of this unit on disorders of consciousness, you should be able to discuss the following: 1. What is the definition of seizure and epilepsy? 2. Describe signs and symptoms in two forms of primary generalized epilepsy.
3. Describe signs and symptoms in two forms of partial epilepsy. 4. Name
systemic disorders which may predispose to seizures.
5. Describe the signs and symptoms associated with syncope. Name two causes of syncope. 6. Describe the utility of EEG-- i.e., is it always diagnostic of epilepsy? Is it specific for any
particular type of epilepsy? Can it be used to aid diagnosis of other conditions?
7. Define status epilepticus. Have a working knowledge of an approach to treating this
8. Have some working knowledge of the appropriate use of the following anticonvulsants (i.e.,
appropriate seizure type, some side effects): Phenytoin, Carbamazepine, Ethosuximide, valproic acid, phenobarbital.
coma. Name 2 supratentorial, 2 infratentorial and 2 global causes of coma.
10. Clinical skill: Be familiar with the physical examination of the comatose patient. B. Getting Started
The objectives for this unit may seem daunting, but they are quite specific. Go first to Chapter 8 of Clinical Neurology and read the introduction to episodic disorders of consciousness on pg. 264. Now, before reading about specific types and causes of epilepsy, a review of the basic sciences mechanisms involved may be helpful (although it is not required). There are several chapters in Human Neurosciences which deal with basic properties of neurons, including Chapters 12 and 13 on membranes, Chapter 14 on membrane potentials, and 15,16 and 17 on
action potentials and synaptic transmission. These are mentioned as references, optional. Now return to your text and read pp. 265-278 on epilepsy. Concentration on pp. 267-271 (seizure classification and EEG) is recommended. Table 8-4 (p.272) should be reviewed primarily for indicated seizure type and side effects. You do not have to memorize it.
C. Self-Assessment You now should have reviewed material relevant to the following subtopics on seizures/syncope:
History/symptoms suggestive of one of these disorders
Etiology (primary neurologic vs. systemic) of seizures
Anticonvulsants: leading drugs, uses, side effects
(We will hold off at the present time on causes of syncope.) Go ahead and try to answer the following review questions without further review. Answers will be provided at the bottom of the exercise. Only one choice is correct. 1. The following factor may be useful in differentiating a seizure from a syncopal episode:
a. The absence of an aura b. The presence of a few jerking movements in a sitting patient c. The association of urinary incontinence with loss of consciousness d. The presence of progressive lightheadedness, dimming out of vision and some
2. Most epilepsy of primary neurologic origin is:
a. Idiopathic b. Caused by mass lesions c. A late-life occurrence d. Associated with mental retardation
3. Systemic disorders which may cause seizures include:
a. Hyper- or hypoglycemia b. Eclampsia c. Alcohol or drug withdrawal d. All of the above
4. Which of the following groupings is incorrect?
a. "Grand mal" and absence ("petit mal") – generalized epilepsy b. Jacksonian march – simple partial epilepsy c. Temporal lobe epilepsy with epigastric aura – simple partial epilepsy d. Jacksonian march with loss of consciousness – simple partial seizure with secondary
5. Which of the following anticonvulsants has the following indications:
carbamazepine Generalized tonic/clonic seizures, complex partial
Juvenile myoclonic epilepsy, generalized tonic/clonic,
6. For which of the following anticonvulsants is the information correct:
Self Assessment answers: 1) d 2) a 3) d 4) c 5) d 6) a Episodic Disorders: Syncope The common thread in syncopal disorders is hypoperfusion to either both cerebral hemispheres or the brainstem. This may be referable to a variety of causes: Orthostatic hypotension, simple faint (vasovagal response), cardiac inflow or outflow problems, cardiac arrhythmias, acute blood loss. Distinctly uncommon is syncope from a primary neurologic cause (e.g., vertebrobasilar TIA). It is useful clinically in distinguishing seizures from syncope to pursue the following: Is there a history of cardiovascular disease, especially arrhythmia? Is the patient's age group and general health likely to preclude a cardiac problem? Do the spells have a stereotypic character or an aura? How long is the period of unconsciousness and is there a post ictal state? Review pp. 278-283 in your text briefly. Areas of concentration should include: cardiovascular syncope (p. 280 on complete heart block) and orthostatic hypotension (p. 282). Episodic Disorders: Coma (The area of coma is covered primarily in Chapter 10 of your text. The following are suggested areas of concentration on this topic.) Coma has been defined as unarousable unresponsiveness. The eyes are usually closed. Coma is not a permanent state. It results from a disturbance--either structural or metabolic--in the brainstem reticular activating system or in both cerebral hemispheres. A. Getting Started
Review pp. 321-322 for immediate management of coma. The key section in Chapter 10 begins on p. 323: Neurologic Examination. Note that the comatose patient's neurologic function is evaluated by examining a series of reflexes and that responses may be symmetric or asymmetric, depending on coma etiology: Pupillary size and reaction Extraocular movements: evaluated by either the Doll's eye maneuver (oculocephalic reflex) or by ice water calorics. (Caloric testing reproduces Doll's eye testing, but is a stronger stimulus.) You should be familiar with the Doll's eye/caloric response in the patient with intact hemispheric function, in the patient with bihemispheric or brainstem injury, in the patient with no brainstem function. Response to pain ("posturing") – review p. 323. The clinical terms of decerebrate and decorticate rigidity are derived from experimental physiology. Anatomically, the precise bases for abnormal motor responses in coma are not precisely defined, however, certain brain regions are identified with certain responses and there is some correlation of motor responses with degree of impairment. Decerebrate rigidity (extensor arm and leg responses) in animals represents damage at the level of the midbrain, in autopsied humans, the correlation is imprecise, but there is typically bilateral and deep diencephalic injury, as seen in trauma, massive hemorrhages or herniation (rostral to caudal deterioration) or an expanding posterior fossa lesion. There may be no structural lesion at all, as in hepatic coma. Decorticate rigidity (arm flexed and leg extended) probably reflects bilateral hemispheric dysfunction and is felt by clinicians to be less ominous. Clinical point: A patient in coma whose exam is asymmetric is more likely to have a structural lesion than a global cause of coma. B. Lesions causing coma Review p. 328, especially herniation syndromes. Neurologists, in practice, are most frequently consulted on patients with metabolic or toxic causes of coma. In the modern hospital setting, anoxic brain damage post cardiac arrest is a frequent cause of coma. Reviewpp. 333-336 on diffuse encephalopathies. Although even patients with non-structural coma can have fluctuations in their responses to the reflex testing reviewed above, lack of focal findings usually implies a global cause of coma (i.e., the toxic/metabolic problems discussed above). The best reference for outside reading on the topic of coma is still: Plum, F. , Posner J.B. : Stupor and Coma, Ed. 3. F. A. Davis Company, Philadelphia, 1980. C. How to evaluate the comatose patient
Please refer to the above material and Chapter 10 in your text for a review of the clinical exam in coma. Please keep the following teaching point in mind when writing your assessment of a comatose patient in the chart: Remember that the point of your note in the chart is to be informative to other physicians and staff who will read it; therefore, it is better to avoid the use of terms which mean different things to different people (e.g., obtunded, "posturing") in favor of rendering a description of what you see. Examples: Informative note: time of exam: 1000
Does not arouse to verbal stimuli or vigorous shaking
Pupils 4mm, briskly reactive; fundi--no papilledema or
Hemorrhage; gags to suction, overbreathes vent
Intact Doll's eyes, corneals intact bilaterally
No spontaneous movement; decorticate posturing to
Sternal rub bilaterally with equal movement of all 4
Limbs; DTR's 2+ throughout, plantars extensor bilat.
Ambiguous note: No time of exam
Patient comatose; pupils 7mm, no eye movements seen
(To what stimulus?); corneals present; withdraws to
Final note: Do not throw the term brain dead around loosely (unless referring to annoying bureaucrats). It has a specific meaning (pp. 337-338), although state laws may have some variation in how to certify brain death.
D. Self-Assessment Quiz
Directions: Choose the one best answer to each question. (Answers are given below.) 1. A 75-year old man with a history of a heart attack a few months previously is sitting at the
breakfast table when he suddenly collapses with loss of consciousness. He states in the emergency department that he had no warning of the episode, was disoriented for about a minute afterwards and feels normal now. Other useful information to be gathered from this
a. A feeling of nausea, some diaphoresis and weakness before the episode b. A description of jerking movements with the episode c. A history of urinary incontinence with the episode d. A history of loss of vision in one eye prior to the episode
2. An 83-year old woman suffers a cardiac arrest at home in the morning; paramedics are
called and begin resuscitative efforts within ten minutes. They are able to re-establish a heart rhythm after ten minutes; they intubate the patient and transport her to the hospital. A neurology consultant is called that evening because the patient has not regained consciousness.
On examination, the patient is unarousable, has symmetric responses to pupillary testing, intact corneal and Doll's eye responses, decorticate posturing on both sides and flexor plantar responses. Which of the following is true?
a. The patient will not regain consciousness. b. The patient is clinically brain dead. c. The patient should be treated with mannitol. d. It is too soon to predict neurologic outcome.
3. A 55 year old man with poorly controlled hypertension collapses and becomes unconscious
after complaining about a headache. He is brought to the emergency department where a neurologic consultant finds the following: BP 220/140, P-70, R-15 and shallow; afebrile, does not arouse to shaking or verbal stimulation; left pupil 7 mm, poorly reactive; R pupil 3 mm and reacts; cold water calorics produce tonic deviation to the left with left injection and no
adduction of the left eye with right injection. The patient most likely has:
a. A structural lesion of the left hemisphere b. A toxic or metabolic encephalopathy c. A structural lesion in the left brainstem d. Hypertensive
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