DD of coma

Diseases that cause no focal or lateralization neurologic signs, usually with normal brainstem functions, CT scan and cellular content of the CSF are normal:
1- Intoxication: alcohol, sedative drugs, opiates, etc
2- Metabolic disturbances: anoxia, hyponatremia, hypernatremia, hypercalcemia, diabetetic acidosis, non ketotic hyperosmolar hyperglycemia, hypoglycemia, uremia, hepatic coma, hypercarbia, addisonian crisis, hypo- and hyperthyroid states, profound nutritional deficiency
3- Sever systemic infections: pneumonia, septicemia, typhoid fever, malaria, water-Friderichsen syndrome
4- Shock from any cause
5- Postseizure states, status epilepticus, subclinical epilepsy
6- Hypertensive encephalopathy, eclampsia
7- Severe hyperthermia, hypothermia
8- Concussion
9- Acute hydrocephalus

Diseases that cause meningeal irritation with or without fever, and with an excess of RBCs or WBCs in the CSF, usually without focal or lateralizing cerebral or brainstem signs, CT or MRI shows no mass lesions:
1- Subarachnoid hemorrhage from ruptured aneurysm, arteriovenous malformation, trauma
2- Acute bacterial meningitis
3- Viral encephalitis
4- Others: Fat embolism, Cholesterol embolism, carcinomatous and lymphomatous meningitis …. Etc

Diseases that cause focal brainstem or lateralizing cerebral signs, with or without changes in CSF, CT and MRI are normal:
1- Hemispheral hemorrhage (basal ganglionic, thalamic) or infarction (large middle cerebral artery territory) with secondary brainstem compression
2- Brainstem infarction due to basilar artery thrombosis or embolism
3- Brain abscess, subdural empyema
4- Epidural and subdural hemorrhage, brain contusion
5- Brain tumor with surrounding edema
6- Cerebellar and pontine hemorrhage and infarction
7- Widespread traumatic brain injury
8- Metabolic coma (as above) with preexisting focal damage
9- Others: 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

DD of coma 2:
1- Trauma:
- Diffuse axonal injury
- Extradural, Subdural memorrhage
- Cerebral contusion
2- Vascular:
- Stroke
- Subarachnoid, intracerebral hemorrhage
- Vasculitis
3- Metabolic:
- Hypothermia
- Hypo- or Hyperglycemia
- Hypo- or hypercalcemia
- Hypo- Hypernatremia
- DKA, hyperosmolar coma
4- Organ failure:
- Cardiac/circulatory failure, cardiac arrest, hypotension
- Respiratory failure with CO2 retention (cerebral hypoxia)
- Liver failure (encephalopathy)
- Renal failure (uremic coma
- Hypothyroidism
5- Toxin/drug induced
- Alcohol
- Overdose (opiates, tricyclics, benzodiazepines)
- Carbon monoxide poisoning
6- Infective:
- Septicemia
- Meningitis
- Encephalitis
- Cerebral malaria
7- Cerebral:
- Cerebral infarction
- Brain tumor
- Brain abscess
- Epilepsy
8- Brainstem lesions:
- Tunors
- Hemorrhage/infarction
- Demylnation (MS)
- Wernick-karsakoff syndrome