NEUROLOGICAL EMERGENCIES

1. NEUROLOGICAL EMERGENCIES

2. Medical coma Traumatic brain injury Acute stroke Delirium Acute behaviour disturbances and their management Tonic-clonic status epilepticus Raised intracranial pressure Management of subarachnoid haemorrhage Cerebral infection Acute spinal cord compression Acute neuromuscular respiratory paralysis Acute visual loss

3. coma

6. The Anatomy and Physiology of Coma Almost all instances of diminished alertness can be traced to widespread abnormalities of the cerebral hemispheres or to reduced activity of a special thalamocortical alerting system termed the reticular activating system (RAS). The proper functioning of this system, its ascending projections to the cortex, and the cortex itself are required to maintain alertness and coherence of thought. It follows that the principal causes of coma are (1) lesions that damage the RAS in the upper midbrain or its projections; (2) destruction of large portions of both cerebral hemispheres; and (3) suppression of reticulocerebral function by drugs, toxins, or metabolic derangements such as hypoglycemia, anoxia, uremia, and hepatic failure. Pupillary enlargement with loss of light reaction and loss of vertical and adduction movements of the eyes suggests that the lesion is in the upper brainstem. Conversely, preservation of pupillary light reactivity and of eye movements absolves the upper brainstem and indicates that widespread structural lesions or metabolic suppression of the cerebral hemispheres is responsible for coma

13. Confusion. “Disturbance of consciousness characterised by impaired capacity to think clearly and to perceive, respond to and remember current stimuli; there is also disorientation.” Confusion involves a generalised disturbance of cortical cerebral function which is usually associated with considerable electroencephalographic (EEG) abnormality. Intervening state between normal consciousness and confusion, that of “clouding of consciousness”.

14. Delirium. “A state of much disturbed consciousness with motor restlessness, transient hallucinations, Disorientation and delusions.” Obtundation . “A disturbance of alertness associated with psychomotor retardation.”

15. Stupor. “A state in which the patient, though not unconscious, exhibits little or no spontaneous activity.” Although the individual appears to be asleep he or she will awaken to vigorous stimulation but show limited motor activities and usually fail to speak. Coma. “A state of unrousable psychologic unresponsiveness in which the subject lies with eyes closed and shows no psychologically understandable response to external stimulus or inner need.” This may be shortened to “a state of unrousable unresponsiveness” which implies both the defect in arousal and in awareness of self or environment manifest as an inability to respond.

16. Vegetative state. “A clinical condition of unawareness of self and environment in which the patient breathes spontaneously, has a stable circulation and shows cycles of eye closure and eye opening which may simulate sleep and waking. This may be a transient stage in the recovery from coma or it may persist until death.” When the cortex of the cerebral hemispheres of the brain recovers more slowly than the brain stem or when the cortex is irreversibly damaged there will arise a situation in which the patient enters a vegetative state without cognitive function. This may be a transient phase through which patients in coma pass as they recover or deteriorate but, commonly after anoxic injuries to the brain, a state develops in which the brain stem recovers function but the cerebral hemispheres are not capable of recovery. This is the “persistent vegetative state”

17. Akinetic mutism. This term has been used to define a similar condition of unresponsiveness but apparent alertness together with reactive alpha and theta EEG rhythms in response to stimuli. The major difference from the vegetative state, in which there is tone in the muscles and extensor or flexor responses, is that patients with akinetic mutism have flaccid tone and are unresponsive to peripheral pain. It is thought that this state is due to bilateral frontal lobe lesions, diffuse cortical lesions, or lesions of the deep grey matter.

18. The locked-in syndrome. a de-efferented state caused by a bilateral ventral pontine lesion involving damage to the cortico-spinal, cortico-pontine, and cortico-bulbar tracts. The patient has total paralysis below the level of the third nerve nuclei and, although able to open, elevate and depress the eyes, has no horizontal eye movements and no other voluntary movements. The diagnosis depends upon the clinician being able to recognise that the patient can open the eyes voluntarily and allow them to close and can signal assent or dissent, responding numerically by allowing the eyelids to fall. Similar states are occasionally seen in patients with severe polyneuropathy, myasthenia gravis, and after the use of neuromuscular blocking agents

19. Pseudo-coma. Rarely, patients who appear in coma without structural, metabolic, toxic, or psychiatric disorder being apparent can be shown by tests of brain stem function to have intact brain stem activity and corticopontine projections and not to be in coma.

20. Coma Due to Metabolic Disorders Cerebral neurons are fully dependent on cerebral blood flow (CBF) and the delivery of oxygen and glucose. CBF is 75 mL per 100g/min in gray matter and 30 mL per 100 g/min in white matter (mean 55 mL per 100 g/min); oxygen consumption is 3.5 mL per 100 g/min, and glucose utilization is 5 mg per 100 g/min. Brain stores of glucose provide energy for 2 minutes after blood flow is interrupted, and oxygen stores last 8–10 seconds after the cessation of blood flow. Simultaneous hypoxia and ischemia exhaust glucose more rapidly. Unlike hypoxia-ischemia, which causes neuronal destruction, most metabolic disorders such as hypoglycemia, hyponatremia, hyperosmolarity, hypercapnia, hypercalcemia, and hepatic and renal failure cause only minor neuropathologic changes. The causes of the reversible effects of these conditions on the brain are not understood but may result from impaired energy supplies, changes in ion fluxes across neuronal membranes, and neurotransmitter abnormalities.

21. Coma and seizures are common accompaniments of large shifts in sodium and water balance in the brain These changes in osmolarity arise from systemic medical disorders, including diabetic ketoacidosis, the nonketotic hyperosmolar state, and hyponatremia from any cause (e.g., water intoxication, excessive secretion of antidiuretic hormone, or atrial natriuretic peptides). Sodium levels <125 mmol/L induce confusion, and <115 mmol/L are associated with coma and convulsions. In hyperosmolar coma, the serum osmolarity is generally >350 mosmol/L. Hypercapnia depresses the level of consciousness in proportion to the rise in carbon dioxide (co2) tension in the blood. In all of these metabolic encephalopathies, the degree of neurologic change depends to a large extent on the rapidity with which the serum changes occur. reflect derangements of CNS biochemistry, membrane function, and neurotransmitters.

24. Differential Diagnosis of Coma • Diseases that cause no focal or lateralizing neurologic signs, usually with normal brainstem functions; CT scan and cellular content of the CSF are normal  a. Intoxications: alcohol, sedative drugs, opiates, etc.      b. Metabolic disturbances: anoxia, hyponatremia, hypernatremia, hypercalcemia, diabetic acidosis, nonketotic hyperosmolar hyperglycemia, hypoglycemia, uremia, hepatic coma, hypercarbia, addisonian crisis, hypo- and hyperthyroid states, profound nutritional deficiency     c. Severe systemic infections: pneumonia, septicemia, typhoid fever, malaria, Waterhouse- Friderichsen syndrome      d. Shock from any cause      e. Postseizure states, status epilepticus, subclinical epilepsy      f. Hypertensive encephalopathy, eclampsia      g. Severe hyperthermia, hypothermia      h. Concussion      i. Acute hydrocephalus

25. 2. Diseases that cause meningeal irritation with or without fever, and with an excess of WBCs or RBCs in the CSF, usually without focal or lateralizing cerebral or brainstem signs; CT or MRI shows no mass lesion      a. Subarachnoid hemorrhage from ruptured aneurysm, arteriovenous malformation, trauma     b. Acute bacterial meningitis      c. Viral encephalitis       d. Miscellaneous: fat embolism, cholesterol embolism, carcinomatous and lymphomatous meningitis, etc.

26. 3. Diseases that cause focal brainstem or lateralizing cere-bral signs, with or without changes in the CSF; CT and MRI are abnormal      a. Hemispheral hemorrhage (basal ganglionic, thalamic) or infarction (large middle cerebral artery territory) with secondary brainstem compression      b. Brainstem infarction due to basilar artery thrombosis or embolism      c. Brain abscess, subdural empyema      d. Epidural and subdural hemorrhage, brain contusion      e. Brain tumor with surrounding edema       f. Cerebellar and pontine hemorrhage and infarction     g. Widespread traumatic brain injury      h. Metabolic coma (see above) with preexisting focal damage      i. Miscellaneous: Cortical vein thrombosis, herpes simplex encephalitis, multiple cerebral emboli due to bacterial endocarditis, acute hemorrhagic leukoencephalitis, acute disseminated (postinfectious) encephalomyelitis, thrombotic thrombocytopenic purpura, cerebral vasculitis, gliomatosis cerebri, pituitary apoplexy, intravascular lymphoma, etc.

27. Approach to the Patient: Coma History In many cases, the cause of coma is immediately evident (e.g., trauma, cardiac arrest, or reported drug ingestion). In the remainder, certain points are especially useful: • the circumstances and rapidity with which neurologic symptoms developed; • the antecedent symptoms (confusion, weakness, headache, fever, seizures, dizziness, double vision, or vomiting); • the use of medications, illicit drugs, or alcohol; and • chronic liver, kidney, lung, heart, or other medical disease. Direct interrogation of family, observers, and ambulance technicians on the scene, in person or by telephone, is an important part of the evaluation.

29. General Physical Examination Fever suggests a systemic infection, bacterial meningitis, encephalitis, heat stroke, neuroleptic malignant syndrome, malignant hyperthermia due to anesthetics or anticholinergic drug intoxication; only rarely is it attributable to a lesion that has disturbed hypothalamic temperature-regulating centers ("central fever"). A slight elevation in temperature may follow vigorous convulsions. Hypothermia is observed with exposure; alcoholic, barbiturate, sedative, or phenothiazine intoxication; hypoglycemia; peripheral circulatory failure; or extreme hypothyroidism. Hypothermia itself causes coma only when the temperature is <31°C (87.8°F). Tachypnea may indicate systemic acidosis or pneumonia or rarely infiltration of the brain with lymphoma. Aberrant respiratory patterns that reflect brainstem disorders are discussed below. Marked hypertension suggests hypertensive encephalopathy, but it may also be secondary to a rapid rise in intracranial pressure (ICP) (the Cushing response) most often after cerebral hemorrhage or head injury.

30. Hypotension is characteristic of coma from alcohol or barbiturate intoxication, internal hemorrhage, myocardial infarction, sepsis, profound hypothyroidism, or Addisonian crisis. The funduscopic examination can detect subarachnoid hemorrhage (subhyaloid hemorrhages), hypertensive encephalopathy (exudates, hemorrhages, vessel-crossing changes, papilledema), and increased ICP (papilledema). Cutaneouspetechiae suggest thrombotic thrombocytopenic purpura, meningococcemia, or a bleeding diathesis associated with an intracerebral hemorrhage. Cyanosis, reddish or anemic skin coloration are other indications of an underlying systemic disease responsible for the coma.

32. Neurologic Examination The patient should first be observed without intervention by the examiner. Tossing about in the bed, reaching up toward the face, crossing legs, yawning, swallowing, coughing, or moaning reflect a drowsy state that is close to normal awakeness. Lack of restless movements on one side or an outturned leg suggests a hemiplegia. Intermittent twitching movements of a foot, finger, or facial muscle may be the only sign of seizures. Multifocal myoclonus almost always indicates a metabolic disorder, particularly uremia, anoxia, drug intoxication (especially with lithium or haloperidol), or a prion disease . In a drowsy and confused patient, bilateral asterixis is a certain sign of metabolic encephalopathy or drug intoxication. Decorticate rigidity and decerebrate rigidity, or "posturing," describe stereotyped arm and leg movements occurring spontaneously or elicited by sensory stimulation.

33. Flexion of the elbows and wrists and supination of the arm (decortication) suggests bilateral damage rostral to the midbrain, whereas extension of the elbows and wrists with pronation (decerebration) indicates damage to motor tracts in the midbrain or caudal diencephalon. The less frequent combination of arm extension with leg flexion or flaccid legs is associated with lesions in the pons. In fact, acute and widespread disorders of any type, regardless of location, frequently cause limb extension, and almost all extensor posturing becomes predominantly flexor as time passes

39. Pupillary Signs Reactive and round pupils of midsize (2.5–5 mm) essentially exclude midbrain damage, either primary or secondary to compression. One enlarged and poorly reactive pupil (>6 mm) signifies compression or stretching of the third nerve from the effects of a cerebral mass above. Enlargement of the pupil contralateral to a hemispheral mass may occur but is infrequent. An oval and slightly eccentric pupil is a transitional sign that accompanies early midbrain–third nerve compression. The most extreme pupillary sign, bilaterally dilated and unreactive pupils, indicates severe midbrain damage, usually from compression by a supratentorial mass. Ingestion of drugs with anticholinergic activity, the use of mydriatic eye drops, and direct ocular trauma are among the causes of misleading pupillary enlargement

43. Ocular Movements Horizontal divergence of the eyes at rest is normal in drowsiness. As coma deepens, the ocular axes may become parallel again. Spontaneous eye movements in coma often take the form of conjugate horizontal roving. This finding alone exonerates damage in the midbrain and pons and has the same significance as normal reflex eye movements . Conjugate horizontal ocular deviation to one side indicates damage to the pons on the opposite side or alternatively, to the frontal lobe on the same side. This phenomenon is summarized by the following maxim: The eyes look toward a hemispheral lesion and away from a brainstem lesion . The eyes may occasionally turn paradoxically away from the side of a deep hemispheral lesion ("wrong-way eyes"). The eyes turn down and inward with thalamic and upper midbrain lesions, typically thalamic hemorrhage. .

44. "Ocular bobbing" describes brisk downward and slow upward movements of the eyes associated with loss of horizontal eye movements and is diagnostic of bilateral pontine damage, usually from thrombosis of the basilar artery. "Ocular dipping" is a slower, arrhythmic downward movement followed by a faster upward movement in patients with normal reflex horizontal gaze; it indicates diffuse cortical anoxic damage Respiratory Patterns These are of less localizing value in comparison to other brainstem signs. Shallow, slow, but regular breathing suggests metabolic or drug depression. Cheyne-Stokes respiration in its classic cyclic form, ending with a brief apneic period, signifies bihemispheral damage or metabolic suppression and commonly accompanies light coma. Rapid, deep (Kussmaul) breathing usually implies metabolic acidosis but may also occur with pontomesencephalic lesions. Tachypnea occurs with lymphoma of the CNS. Agonal gasps are the result of lower brainstem (medullary) damage and are recognized as the terminal respiratory pattern of severe brain damage.

45. Laboratory Studies and Imaging chemical-toxicologic analysis of blood and urine, cranial CT or MRI, EEG, and CSF examination. Arterial blood gas analysis Toxicologic analysis The EEG Lumbar puncture . Blood culture

48. Treatment: Coma The immediate goal in a comatose patient is prevention of further nervous system damage. Hypotension, hypoglycemia, hypercalcemia, hypoxia, hypercapnia, and hyperthermia should be corrected rapidly. An oropharyngeal airway is adequate to keep the pharynx open in a drowsy patient who is breathing normally. Tracheal intubation is indicated if there is apnea, upper airway obstruction, hypoventilation, or emesis, or if the patient is liable to aspirate because of coma. Mechanical ventilation is required if there is hypoventilation or a need to induce hypocapnia in order to lower ICP. IV access is established, and naloxone and dextrose are administered if narcotic overdose or hypoglycemia are possibilities; thiamine is given along with glucose to avoid provoking Wernicke's disease in malnourished patients. In cases of suspected basilar thrombosis with brainstem ischemia, IV heparin or a thrombolytic agent is often utilized, after cerebral hemorrhage has been excluded by a neuroimaging study.

50. The use of benzodiazepine antagonists offers some prospect of improvement after overdose of soporific drugs and has transient benefit in hepatic encephalopathy. Administration of hypotonic solutions should be monitored carefully in any serious acute brain illness because of the potential for exacerbating brain swelling. Cervical spine injuries must not be overlooked, particularly before attempting intubation or evaluation of oculocephalic responses. Fever and meningismus indicate an urgent need for examination of the CSF to diagnose meningitis. If the lumbar puncture in a case of suspected meningitis is delayed, an antibiotic such as a third-generation cephalosporin may be administered, preferably after obtaining blood cultures.