Subarachnoid hemorrhage differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Syed Ahsan Hussain, M.D.[2] Sara Mehrsefat, M.D. [3]

Differential diagnosis

It is clinically difficult to distinguish subarchnoid hemorrhage from an ischemic stroke. However, the symptoms like headache, nausea, vomiting, and depressed level of consciousness should raise the suspicion for a hemorrhagic event compared to ischemic stroke.

Disease	Findings
Ischemic stroke	Occurs when a clot or a mass clogs a blood vessel and cutting off the blood flow to the brain Present as a Thrombotic stroke (thrombus develops at the clogged part of the vessel) Embolic strokes (blood clot that forms at another locations usually the heart and large arteries of the upper chest and neck, and travels to the brain) Urgent evaluation with brain / neurovascular imaging (such as MRI, CT, CTA, MRA), cardiac, and metabolic evaluation is often necessary
transient ischemic attack (TIA)	Caused by a temporary clot which often called a “mini stroke” Occurs rapidly and presents as a sudden onset of a focal neurologic symptom/sign lasting less than 24 hours Urgent evaluation with brain / neurovascular imaging (such as MRI, CT, CTA, MRA), cardiac, and metabolic evaluation is often necessary
Acute hypertensive crisis/Malignant hypertension	Presents as significantly elevated blood pressure (systolic pressure ≥180 and/or diastolic pressure ≥120 mmHg) with or wihout acute end-organ injury Urgent evaluation with MRI and CT of the brain, serum creatinine, urinalysis, cardiac (EKG, chest x ray, and cardiac enzymes) and metabolic evaluation is often necessary
Sentinel headache	Caused by small aneurysmal leaks into the subarachnoid space Presents as a episode of headache similar to that accompanying subarachnoid hemorrhage (days to weeks prior to aneurysm rupture) and focal neurologic symptoms and signs are usually absent
Sinusitis	Presents with acute and subacute headaches and facial pain
Hypoglycemia
Pituitary apoplexy	Caused by pituitary gland infarct or hemorrhage secondary to pitutiery adenoma Presents with acute headache, change in mental status, ophthalmoplegia, and decreased visual acuity Brain CT and MRI are the preferred imaging techniques
Cerebral venous thrombosis	Presents with isolated gradual onset headache or in combination with papilledema, seizures, bilateral focal deficits, and change in mental status Brain MRI with venography should be considered
Colloid cyst of the third ventricle	Caused by an acute obstructive hydrocephalus secondary to sudden obstruction in cerebrospinal fluid flow by the cyst Presents with an acute onset fronto-parietal or fronto-occipital headache which relieved by taking the supine position and may be associated with nausea, vomiting, mental status changes, seizures, coma Head CT or MRI of the brain are usually diagnostic
Cervical artery dissection	It usulay occurs spontaneously or after head and neck injury Presents with gradual onset head and neck pain with a local manifestations (such as Horner syndrome, pulsatile tinnitus, bruit, or cranial neuropathies) Neuroimagings are usually preferred (brain MRI with MRA and cranial CT with CTA)
Reversible cerebral vasoconstriction syndrome	Occurs spontaneously and trigerred by sexual activity, exertion, emotion, and constriction of the cerebral arteries Presents with acute severe headache with or without focal deficits or seizures that resolves spontaneously within 12 weeks
Spontaneous intracranial hypotension	Presents with orthostatic headaches, nausea, vomiting, dizziness, diplopia, interscapular pain Caused by cerebrospinal fluid (CSF) leakage from spinal meningeal defects or dural tears Brain MRI is the preferred imaging techniques

Diseases	Diagnostic tests				Physical Examination					Symptoms			Past medical history	Other Findings
	Na+, K+, Ca2+	CT /MRI	CSF Findings	Gold standard test	Neck stiffness	Motor or Sensory deficit	Papilledema	Bulging fontanelle	Cranial nerves	Headache	Fever	Altered mental status
Brain tumour		✔	Cancer cells	MRI		✔	✔	✔	✔	✔		✔		Cachexia, gradual progression of symptoms
Delirium tremens		✔		Clinical diagnosis		✔	✔		✔	✔	✔	✔	Alcohol intake, sudden witdrawl or reduction in consumption	Tachycardia, diaphoresis, hypertension, tremors, mydriasis, positional nystagmus,
Subarachnoid hemorrhage		✔	Xanthochromia	CT scan without contrast	✔	✔	✔	✔	✔	✔	✔	✔	Trauma/fall	Confusion, dizziness, nausea, vomiting
Stroke		✔	Normal	CT scan without contrast		✔	✔		✔	✔		✔	TIAs, hypertension, diabetes mellitus	Speech difficulty, gait abnormality
Neurosyphilis		✔	↑ Leukocytes and protein	CSF VDRL-specifc CSF FTA-Ab -sensitive	✔	✔	✔	✔		✔		✔	Unprotected sexual intercourse, STIs	Blindness, confusion, depression, Abnormal gait
Viral encephalitis		✔	Increased RBCS or xanthochromia, mononuclear lymphocytosis, high protein content, normal glucose	Clinical assesment	✔	✔	✔		✔	✔	✔	✔	Tick bite/mosquito bite/ viral prodome for several days	Extreme lethargy, rash hepatosplenomegaly, lymphadenopathy, behavioural changes
Herpes simplex encephalitis		✔		Clinical assesment			✔	✔	✔	✔	✔		History of hypertension	Delirium, cortical blindness, cerebral edema, seizure
Wernicke’s encephalopathy			Normal				✔	✔			✔		History of alcohal abuse	Ophthalmoplegia, confusion
CNS abscess		✔	↑ leukocytes >100,000/ul, ↓ glucose and ↑ protien, ↑ red blood cells, lactic acid >500mg	Contrast enhanced MRI is more sensitive and specific, Histopathological examination of brain tissue	✔	✔	✔		✔	✔	✔	✔	History of drug abuse, endocarditis, ↓ immune status	High grade fever, fatigue,nausea, vomiting
Drug toxicity											✔	✔		Lithium, Sedatives, phenytoin, carbamazepine
Conversion disorder				Diagnosis of exclusion		✔		✔		✔	✔	✔		Tremors, blindness, difficulty swallowing
Electrolyte disturbance	↓ or ↑			Depends on the cause						✔		✔		Confusion, seizures
Febrile convulsion			Not performed in first simple febrile seizures	Clinical diagnosis and EEG					✔	✔	✔	✔	Family history of febrile seizures, viral illness or gastroenteritis	Age > 1 month,
Subdural empyema		✔		Clinical assesment and MRI	✔	✔	✔	✔	✔			✔	History of relapses and remissions	Blurry vision, urinary incontinence, fatigue
Hypoglycemia	↓ or ↑			Serum blood glucose HbA1c		✔				✔		✔	History of diabetes	Palpitations, sweating, dizziness, low serum, glucose

Subarachnoid hemorrhage should be differentiated from other diseases causing severe headache for example:

Disease	Symptoms	Diagnosis
		CT/MRI	Other Investigation Findings
Subarachnoid hemorrhage	Severe headache (as a worst headache of the life) Headache is the main symptom (often starts suddenly and starts after a popping or snapping feeling in the head) Double vision Nausea and vomiting Symptoms of meningeal irritation Sudden decreased level of consciousness Rapid progression of symptoms	The modality of choice for diagnosis of subarachnoid hemorrhage is noncontrast head computed tomography (CT), with or without lumbar puncture.[1] CT shows hyperattenuating material filling the subarachnoid space.	Lumbar puncture (LP) is necessary when there is a strong suspicion of subarachnoid hemorrhage. LP will show: Elevated opening pressure Elevated red blood cell (RBC) Xanthochromia
Meningitis	Headache   Neck stiffness Fever Photophobia (inability to tolerate bright light) Phonophobia (inability to tolerate loud noises)  Irritability, altered mental status (in small children)	CT scan of the head may be performed before LP to determine the risk of herniation.	Diagnosis is based on clinical presentation in combination with CSF analysis. CSF analysis is the investigation of choice. For more information on CSF analysis in meningitis please click here.
Intracranial mass	Headache Nausea Vomiting Change in mental status Seizures Focal symptoms of brain damage Associated co-morbid conditions like tuberculosis, etc	CT or MRI is the initial test to detect intracranial lesions. These imaging tests determine the location of intracranial mass lesion(s) and help in guiding therapy.	Biopsy of the lesion is needed to identify the nature of the lesion such as: Tumor Abscess X- ray of the skull is a non specific test, but useful if any of the lesions are calcified.
Cerebral hemorrhage	Headache, vomiting, and depressed level of consciousness from increased intracranial pressure (ICP)   Progression of focal neurological deficits over periods of hours	CT scan without contrast is the initial test performed to diagnose ischemic stroke and rule out hemorrhagic stroke. CT is very sensitive for identifying acute hemorrhage which appears as hyperattenuating clot. Gradient echo and T2 susceptibility-weighted MRI are as sensitive as CT for detection of acute hemorrhage and are more sensitive for identification of prior hemorrhage.	PT/ INR and aPTT should be checked to rule out coagulopathy.
Cerebral Infarction	The symptoms of an ischemic stroke vary widely depending on the site and blood supply of the area involved. For more information on symptoms of ischemic stroke based on area involved please click here.	CT scan without contrast is the initial test performed to diagnose ischemic stroke and rule out hemorrhagic stroke. CT may show hypo-attenuation and swelling of involved area. MR diffusion weighted imaging is the most sensitive and specific test for diagnosing ischemic stroke and may help detect presence of infarction in few minutes of onset of symptoms.	Carotid doppler may be done to check for patency of carotid arteries and blood supply to the brain. Cerebral angiogram is an invasive test and detect abnormalities of the blood vessels, including narrowing, blockage, or malformations (such as aneurysms or arterio-venous malformations).
Intracranial venous thrombosis	Headache: It is a common presentation (present in 90% of cases); it tends to worsen over a period of several days, but may also develop suddenly (thunderclap headache).[1] The headache may be the only symptom of cerebral venous sinus thrombosis.[2] Inability to move one or more limbs. Weakness on one side of the face. Seizures: 40% of all patients have seizure. Depressed level of consciousness and otherwise unexplained changes in mental status are common symptoms in the elderly.[4]	The classic finding of sinus thrombosis on unenhanced CT images is a hyperattenuating thrombus in the occluded sinus. CT and MRI may identify Cerebral edema and venous infarction may be apparent.	CT venography detects the thrombus, computed tomography with radiocontrast in the venous phase (CT venography or CTV) has a detection rate that in some regards exceeds that of MRI. Cerebral angiography may demonstrate smaller clots, and obstructed veins may give the "corkscrew appearance".
Migraine	Severe or moderate headache (which is often one-sided and pulsating) lasts between several hours to three days. Other symptoms include gastrointestinal upsets, such as nausea and vomiting, and a heightened sensitivity to bright lights (photophobia) and noise (phonophobia). Approximately one third of people who experience migraine get a preceding aura.[4]	CT and MRI may be needed to rule out other suspected possible causes of headache.	Migraine is a clinical diagnosis that does not require any laboratory tests. Laboratory tests can be ordered to rule out any suspected coexistent metabolic problems or to determine the baseline status of the patient before initiation of migraine therapy.
Head injury	Headache Confusion Drowsiness Personality change Seizures Nausea and vomiting Loss of consciousness lucid interval	CT scan is the first test performed and identifies cerebral hemorrhage (appears as hyperattenuating clot) following head injury. CT scan is also less time consuming. MRI is more sensitive, takes more time and is done in patients with symptoms unexplained by CT scan.	The Glasgow Coma Scale is a tool for measuring degree of unconsciousness and is thus a useful tool for determining severity of injury. The Pediatric Glasgow Coma Scale is used in young children.
Lymphocytic hypophysitis	Lymphocytic hypophysitis is most often seen in late pregnancy or the postpartum period with the following symptoms: Hypopituitarism Mass lesion effect such as headache or visual field defects	CT & MRI typically reveal features of a pituitary mass.	The most accurate test is pituitary biopsy which will show lymphocytic infiltration.
Radiation injury	Headache Impairment of mental function is the most prominent feature such as personality change, impairment of memory, confusion, learning difficulties. Focal neurological abnormalities and evidence of raised intracranial pressure.	CT & MRI will show: Focal radiation necrosis Diffuse white matter injury Contrast-enhancing mass surrounded by edema and mass effect	PET scan Radiation necrosis is hypo metabolic and will have decreased uptake of fluorodeoxyglucose.