Clinical diagnosis
Evaluate for underlying etiology
Standard approach:
Head CT
LP (if not contraindicated by CT findings) with opening and closing pressures
Head CT
LP (if not contraindicated by CT findings) with opening and closing pressures
Bulging fontanelle
Meningitis
Periorbital swelling
Encephalitis
Stridor
Meningoencephalitis
Stridor 
Congestive Heart Failure