Rabies differential diagnosis
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
The differential diagnosis for rabies deals with eliminating diseases with similar symptoms from the diagnosis. There are many viruses that can appear similar to rabies such as encephalitis and the herpes simplex virus. It is very important to rule out certain diseases such as echovirus and poliovirus. Rabies is a serious disease that needs to be treated quickly if someone is suspected to be infected with the virus.
Differentiating Rabies from other Diseases
Rabies should be differentiated from other causes of headache and decrease consciousness:
| Diseases | History and Physical | Diagnostic tests | Other Findings | |||||
|---|---|---|---|---|---|---|---|---|
| Prodromal symptoms | Fever | Headache | LOC | Neuro Onset | Laboratory Findings | Imaging preferance | ||
| Rabies infection | + | + | + | + | Insidious | Antibody detection in serology
Skin biopsy of injured skin |
MRI | Hydrophobia, aerophobia, dysphagia, and localized pain, weakness or paresthesias |
| Meningitis | + | + | + | - | Sudden | CSF analysis:
↑ Protein ↓ Glucose |
CT scan: First choice
MRI: Best choice |
Fever, neck, rigidity |
| encephalitis | + | + | + | + | Sudden | PCR
CSF analysis and culture reveal the responsible micro-organism |
MRI | Accompany a meningoencephalitis, seizures, hemiparesis, cranial nerve palsies, photophobia, nausea |
| Autoimmune encephalitis | - | +/- | + | +/- | Insidious | Autoantibodies present in both serum and CSF | MRI
EEG |
Memory deficit, dyskinesias, seizures, autonomic instability |
| CNS abscess | + | + | + | + | Insidious | CSF analysis:
↓ Glucose ↑ Protein |
MRI is more sensitive and specific | High grade fever, fatigue,nausea, vomiting |
| Poliomyelitis | + | + | + | + | Sudden | PCR of CSF | MRI | Asymmetric paralysis following a flu-like syndrome |
| Neurosyphilis | - | - | + | + | Insidious | CSF VDRL-specifc | MRI & Lumbar puncture | History of unprotected sex or multiple sexual partners, and genital ulcer (chancre)
Blindness, confusion, depression, abnormal gait |
| Tick paralysis (Dermacentor tick) | - | - | +/- | +/- | Insidious | - | - | History of outdoor activity in Northeastern United States
Tick often still latched to the patient at presentation (often in head and neck area) |
| Botulism | - | - | - | - | Sudden | Toxin test, blood, wound, or stool culture | - | Diplopia, Hyporeflexia, Hypotonia, possible respiratory paralysis, Floppy baby syndrome |
| Tetrodotoxin poisoning | - | - | +/- | +/- | Sudden | - | - | History of consumption of puffer fish species |
| Metabolic disturbances (electrolyte imbalance, hypoglycemia) | - | +/- | - | + | Sudden | Hypoglycemia, hypo and hypernatremia | MRI | Confusion, seizure, palpitations, sweating, dizziness, hypoglycemia |
| Electrolyte disturbance | - | - | - | +/- | Insidious | Hypocalcemia, hypomagnesemia, hypo- or hyperkalemia | Possible arrhythmia | |
| Drug toxicity/Neuroleptic malignant syndrome | - | + | - | + | Sudden | Elevated serum creatine kianse
Hypocalcemia, hypomagnesemia, hypo- and hypernatremia, hyperkalemia, and metabolic acidosis |
Generalized slow wave EEG | Causative medications (eg, neuroleptics, antiemetics, concomitant lithium), dopaminergic withdrawal
Mental status change, rigidity, or dysautonomia |
| Organophosphate toxicity | - | - | - | + | Sudden | Clinical suspicion confirmed with RBC AchE activity | - | History of exposure to insecticide or living in farming environment with : Diarrhea, Miosis, Bradycardia, Lacrimation, Emesis, Salivation, Sweating |
| Ischemic stroke | - | - | +/- | + | Sudden | - | MRI for ischemia | Sudden unilateral motor and sensory deficit in a patient with a history of atherosclerotic risk factors (diabetes, hypertension, smoking) or atrial fibrillation |
| Hemorrhagic stroke | - | - | + | + | Sudden | - | CT scan without contrast | Neck stiffness |
| Subdural hemorrhage | - | - | + | + | Sudden | CSF analysis:
Xanthochromia |
CT scan without contrast | Confusion, dizziness, nausea, vomiting |
| Hypertensive encephalopathy | - | - | + | + | Sudden | - | - | Delirium, cortical blindness, cerebral edema, seizure |
| Wernicke’s encephalopathy | - | - | - | + | Sudden | - | - | Ophthalmoplegia, confusion |
| Amyotrophic lateral sclerosis | - | - | +/- | +/- | Insidious | Normal LP (to rule out DDx) | MRI | Patient initially presents with upper motor neuron deficit (spasticity) followed by lower motor neuron deficit (flaccidity) |
| Diffuse gliomatosis | - | - | + | - | Insidious | Cancer specific molecular characteristics
Normal CSF |
MRI (expansile, T2 hyperintense lesion) | Seizures, memory loss, motor weakness, visual symptoms, language deficit, and cognitive and personality changes |
| Central nervous system lymphoma | + | - | + | +/- | Insidious | CSF cytology, flow cytometry, and stereotactic brain biopsy | MRI (parenchymal or leptomeningeal enhancement) | Associated with immunodeficiency
Focal neurological deficits, neuropsychiatric symptoms, signs of raised intracranial pressure, seizures, and ocular symptoms |
The most important differential diagnosis when it comes to the rabies presentations include meningitis and encephalitis. It is important to differentiate different rabies from each one of the causes of meningitis/encephalitis, which may differ based on the season of occurrence and the geographical region.
The most important viruses to rule out are:
- Herpes simplex virus type 1
- Varicella-zoster virus
- (Less commonly) Enteroviruses including:
- Coxsackieviruses
- Echoviruses
- Polioviruses
- Human enteroviruses 68 to 71.
In addition, consideration should be given to the local epidemiology of encephalitis caused by arboviruses belonging to several taxonomic groups, including:
- Eastern equine encephalitis viruses
- Western equine encephalitis viruses
- St. Louis encephalitis virus
- Powassan virus
- The California encephalitis virus serogroup
- La Crosse virus.
New causes of viral encephalitis are also possible, as was evidenced by the recent outbreak in Malaysia of some 300 cases of encephalitis (mortality rate, 40%) caused by Nipah virus, a newly recognized paramyxovirus. Similarly, well-known viruses may be introduced into new locations, as is illustrated by the recent outbreak of encephalitis due to West Nile virus in the eastern United States. Epidemiologic factors (e.g., season, geographic location, and the patient’s age, travel history, and possible exposure to animal bites, rodents, and ticks) may help direct the diagnostic workup.