Symptom Finder - Convulsions
CONVULSIONS
To formulate a differential diagnosis of convulsions, one must use both
physiology and anatomy.
Irritability of the nerve cell is caused by the same physiologic factors that lead to irritability of a muscle cell: anoxia, hypoglycemia, and electrolyte imbalances. Any condition causing anoxia may cause a seizure; thus, focal arterial spasm (e.g., transient ischemic attack [TIA]) may lead to seizures. Obstruction of the artery by emboli, thrombi, or atheromatous plaques may cause focal anoxia and seizures, whereas diffuse cerebral
anoxia is more likely to cause syncope and coma. Acute blood loss (anemic anoxia) and acute reduction in cardiac output (as in Stokes– Adams disease and various arrhythmias) are infrequent causes of seizures.
Aortic stenosis and insufficiency may occasionally cause seizures by relative reduction in cardiac output compared to demand (as during exercise).
Hypoglycemia is more likely to cause a coma than a seizure. Anything that severely reduces the blood sugar (<40 mg/dL), such as exogenous insulin overdose, islet cell adenoma, Addison disease, and hypopituitarism, may cause a seizure.
Irritability of the nerve cell is more often caused by electrolyte alterations.
Hypocalcemia may at first lead to tetany, simulating a convulsion. The causes of hypocalcemia include hypoparathyroidism, vitamin D deficiency, malabsorption syndrome, calcium-losing nephropathy, and chronic nephritis. Ionizable calcium is decreased by alkalosis, respiratory or metabolic. Hypomagnesemia must be ruled out, especially in chronic alcoholics and in malabsorption syndromes. Water intoxication should be considered in inappropriate antidiuretic hormone (ADH) syndrome (relative dilution of both calcium and magnesium).
Moving from the physiologic causes of seizures to the anatomic analysis, the physician’s main consideration is that something mechanical is irritating the nerve cell. The nerve cell may be irritated by a tumor of the supporting tissue, an abscess, or a hematoma. Pressure from inflammatory lesions in the meninges (i.e., meningitis or epidural abscess) or hemorrhage into this layer (subdural or epidural hematoma and subarachnoid hemorrhages) may be the mechanical irritant. Focal accumulation of fluid in the brain substance as in encephalitis, concussions, and increased intracranial pressure from whatever causes may lead to a seizure.
A depressed skull fracture is occasionally the mechanical irritant, as is a scar from an old skull injury. Infiltration of the brain by metals such as lead and copper (i.e., Wilson disease) are worth considering in children, particularly infiltration of the brain by a foreign cell (i.e., leukemia). Reticuloendotheliosis and mucopolysaccharidosis should be considered. Turning to exogenous factors, one must consider a host of chemicals and drugs that may cause seizures, most commonly alcohol, paint thinners, lidocaine (Xylocaine), phenothiazine drugs, and bromides. A bolus of almost any substance may occasionally cause seizures if it is large enough.
Occasionally, degenerative and demyelinating disease may present with seizures. In contrast, lupus erythematosus and other collagen diseases may frequently present with seizures. Finally, one should not forget idiopathic epilepsy.
Approach to the Diagnosis
The first thing to do is ascertain whether the motor disturbance or episode of loss of consciousness was really a seizure. Hysterical seizures are not associated with incontinence or tongue biting. There is often an aura with real seizures but not so with hysterical seizures. A serum prolactin should be done because it is only elevated in real seizures. Another way to rule out hysterical seizures is have a member of the family take a video of the patient during a seizure.
Next, a careful history from the immediate family or friend is important. Be sure to ask about previous head trauma (including birth trauma), anoxia, meningitis, or encephalitis. Inquiry into drug or alcohol abuse is essential.
A thorough neurologic examination is a must. If the clinician is too busy or not equipped to do this, referral to a neurologist is done at this point. If there are focal neurologic signs or papilledema, there is a strong chance that the patient has a space-occupying lesion such as tumor, subdural hematoma, or abscess and will need a neurologist anyway.
The clinical picture will help determine the cause of the seizures. If there is alcohol or drug use, toxic encephalopathy is suspected. If there is fever, meningitis or encephalitis must be considered in the differential diagnosis. If there is a heart murmur or irregular heartbeat, cerebral embolism should be suspected. A history of trauma suggests posttraumatic epilepsy. A history of optic neuritis makes one suspicious of multiple sclerosis. A history of high-risk sexual behavior suggests that acquired immunodeficiency syndrome (AIDS) may be the cause. A history of cancer makes it important to rule out cerebral metastasis. The initial workup should include a CBC, urinalysis, sedimentation rate, ANA, VDRL test, chemistry panel, drug screen, wake-and-sleep EEG, and skull x-ray. Patients with suspected grand mal epilepsy or focal motor seizures need either a CT scan or MRI to rule out a space-occupying
lesion.
This is true of all patients with complex partial seizures as well. Patients suspected of having meningitis or encephalitis need a spinal tap. Patients with possible cerebral embolism need an ECG, echocardiogram, blood cultures, and a cardiology consult. If AIDS is suspected, a human immunodeficiency virus (HIV) antibody titer is ordered. Patients with possible multiple sclerosis need a spinal fluid analysis, and visual, somatosensory, or brainstem-evoked potential studies. Elderly patients should have a chest x-ray done to exclude a primary tumor of the lung.
Other Useful Tests
1. Holter monitoring (heart block)
2. Ambulatory EEG monitoring (epilepsy with infrequent seizures)
3. 72-hour fast (hypoglycemia)
4. 24-hour urine calcium (hypoparathyroidism)
5. Stool for ova and parasites (cysticercosis)
6. Urine porphobilinogen (porphyria)
7. Blood lead level (lead encephalopathy)
8. Therapeutic trial of anticonvulsants
To formulate a differential diagnosis of convulsions, one must use both
physiology and anatomy.
Irritability of the nerve cell is caused by the same physiologic factors that lead to irritability of a muscle cell: anoxia, hypoglycemia, and electrolyte imbalances. Any condition causing anoxia may cause a seizure; thus, focal arterial spasm (e.g., transient ischemic attack [TIA]) may lead to seizures. Obstruction of the artery by emboli, thrombi, or atheromatous plaques may cause focal anoxia and seizures, whereas diffuse cerebral
anoxia is more likely to cause syncope and coma. Acute blood loss (anemic anoxia) and acute reduction in cardiac output (as in Stokes– Adams disease and various arrhythmias) are infrequent causes of seizures.
Aortic stenosis and insufficiency may occasionally cause seizures by relative reduction in cardiac output compared to demand (as during exercise).
Hypoglycemia is more likely to cause a coma than a seizure. Anything that severely reduces the blood sugar (<40 mg/dL), such as exogenous insulin overdose, islet cell adenoma, Addison disease, and hypopituitarism, may cause a seizure.
Irritability of the nerve cell is more often caused by electrolyte alterations.
Hypocalcemia may at first lead to tetany, simulating a convulsion. The causes of hypocalcemia include hypoparathyroidism, vitamin D deficiency, malabsorption syndrome, calcium-losing nephropathy, and chronic nephritis. Ionizable calcium is decreased by alkalosis, respiratory or metabolic. Hypomagnesemia must be ruled out, especially in chronic alcoholics and in malabsorption syndromes. Water intoxication should be considered in inappropriate antidiuretic hormone (ADH) syndrome (relative dilution of both calcium and magnesium).
Moving from the physiologic causes of seizures to the anatomic analysis, the physician’s main consideration is that something mechanical is irritating the nerve cell. The nerve cell may be irritated by a tumor of the supporting tissue, an abscess, or a hematoma. Pressure from inflammatory lesions in the meninges (i.e., meningitis or epidural abscess) or hemorrhage into this layer (subdural or epidural hematoma and subarachnoid hemorrhages) may be the mechanical irritant. Focal accumulation of fluid in the brain substance as in encephalitis, concussions, and increased intracranial pressure from whatever causes may lead to a seizure.
A depressed skull fracture is occasionally the mechanical irritant, as is a scar from an old skull injury. Infiltration of the brain by metals such as lead and copper (i.e., Wilson disease) are worth considering in children, particularly infiltration of the brain by a foreign cell (i.e., leukemia). Reticuloendotheliosis and mucopolysaccharidosis should be considered. Turning to exogenous factors, one must consider a host of chemicals and drugs that may cause seizures, most commonly alcohol, paint thinners, lidocaine (Xylocaine), phenothiazine drugs, and bromides. A bolus of almost any substance may occasionally cause seizures if it is large enough.
Occasionally, degenerative and demyelinating disease may present with seizures. In contrast, lupus erythematosus and other collagen diseases may frequently present with seizures. Finally, one should not forget idiopathic epilepsy.
Approach to the Diagnosis
The first thing to do is ascertain whether the motor disturbance or episode of loss of consciousness was really a seizure. Hysterical seizures are not associated with incontinence or tongue biting. There is often an aura with real seizures but not so with hysterical seizures. A serum prolactin should be done because it is only elevated in real seizures. Another way to rule out hysterical seizures is have a member of the family take a video of the patient during a seizure.
Next, a careful history from the immediate family or friend is important. Be sure to ask about previous head trauma (including birth trauma), anoxia, meningitis, or encephalitis. Inquiry into drug or alcohol abuse is essential.
A thorough neurologic examination is a must. If the clinician is too busy or not equipped to do this, referral to a neurologist is done at this point. If there are focal neurologic signs or papilledema, there is a strong chance that the patient has a space-occupying lesion such as tumor, subdural hematoma, or abscess and will need a neurologist anyway.
The clinical picture will help determine the cause of the seizures. If there is alcohol or drug use, toxic encephalopathy is suspected. If there is fever, meningitis or encephalitis must be considered in the differential diagnosis. If there is a heart murmur or irregular heartbeat, cerebral embolism should be suspected. A history of trauma suggests posttraumatic epilepsy. A history of optic neuritis makes one suspicious of multiple sclerosis. A history of high-risk sexual behavior suggests that acquired immunodeficiency syndrome (AIDS) may be the cause. A history of cancer makes it important to rule out cerebral metastasis. The initial workup should include a CBC, urinalysis, sedimentation rate, ANA, VDRL test, chemistry panel, drug screen, wake-and-sleep EEG, and skull x-ray. Patients with suspected grand mal epilepsy or focal motor seizures need either a CT scan or MRI to rule out a space-occupying
lesion.
This is true of all patients with complex partial seizures as well. Patients suspected of having meningitis or encephalitis need a spinal tap. Patients with possible cerebral embolism need an ECG, echocardiogram, blood cultures, and a cardiology consult. If AIDS is suspected, a human immunodeficiency virus (HIV) antibody titer is ordered. Patients with possible multiple sclerosis need a spinal fluid analysis, and visual, somatosensory, or brainstem-evoked potential studies. Elderly patients should have a chest x-ray done to exclude a primary tumor of the lung.
Other Useful Tests
1. Holter monitoring (heart block)
2. Ambulatory EEG monitoring (epilepsy with infrequent seizures)
3. 72-hour fast (hypoglycemia)
4. 24-hour urine calcium (hypoparathyroidism)
5. Stool for ova and parasites (cysticercosis)
6. Urine porphobilinogen (porphyria)
7. Blood lead level (lead encephalopathy)
8. Therapeutic trial of anticonvulsants