Viral Upper Respiratory Infection (URTI): This is the most common cause of nasal discharge and can be associated with stiffness in the neck due to muscle strain or referred pain from the throat. Justification: High prevalence, matches symptoms.

Bacterial Sinusitis: Can cause purulent nasal discharge and neck stiffness due to inflammation of the sinuses. Justification: Common condition, symptoms align.
Allergic Rhinitis: May cause nasal discharge and could lead to neck stiffness due to chronic strain from nose blowing or discomfort. Justification: Common, especially in allergy seasons or in individuals with known allergies.
Pharyngitis: Inflammation of the throat can cause discomfort that might lead to neck stiffness, and postnasal drip can cause nasal discharge. Justification: Common condition, symptoms can overlap.

Meningitis: Although less common, it is critical to consider due to its high morbidity and mortality. Symptoms can include neck stiffness (often severe), fever, and sometimes nasal discharge if there's an associated upper respiratory infection. Justification: Potentially life-threatening, requires immediate intervention.
Subarachnoid Hemorrhage: Can present with sudden severe headache and neck stiffness. While nasal discharge is not a primary symptom, it could be present if there's an associated condition. Justification: Emergency condition, critical to diagnose promptly.
Encephalitis: Inflammation of the brain, which can cause a variety of symptoms including fever, headache, and sometimes neck stiffness. Nasal discharge might not be a primary symptom but could be present in some cases. Justification: Serious condition requiring prompt diagnosis and treatment.

CSF Leak: A condition where cerebrospinal fluid leaks into the nasal passages, potentially causing clear nasal discharge. Neck stiffness could be associated if there's an underlying condition like a tumor or trauma. Justification: Uncommon, specific diagnostic tests are required.
Tuberculous Meningitis: A rare condition in many parts of the world, characterized by chronic meningitis caused by tuberculosis. Symptoms can include neck stiffness, fever, and potentially nasal discharge if there's an associated sinus infection. Justification: Rare, but important to consider in endemic areas or in individuals with risk factors.
Fungal Sinusitis: Can cause nasal discharge and, in severe cases, invade surrounding structures leading to symptoms like neck stiffness. Justification: Uncommon, more likely in immunocompromised individuals.