• Do not drive himself.
• Have someone stay with him if possible.
• Bring a list of symptoms, timing of the hand weakness/headaches, weight change, medications/substances, and any recent injury.
• Avoid self-treating with sedatives, stimulants, recreational drugs, or excess caffeine.

Priority differential diagnosis

1. Neurologic and vascular conditions to rule out urgently

• Ischemic stroke or transient ischemic attack (TIA), despite young age. Causes in younger people include arterial dissection, clotting disorders, cardiac sources, or drug/stimulant use.
• Carotid or vertebral artery dissection, particularly relevant with headache plus neck pain and a focal limb deficit. This can follow even relatively minor neck trauma or sudden neck movements.
• Cerebral venous sinus thrombosis (CVST), which can cause progressive headache, raised intracranial pressure, focal weakness, seizures, or visual symptoms.
• Intracranial mass lesion, such as a brain tumor, abscess, or less commonly another space-occupying lesion. Headache and focal weakness can occur together.
• Raised intracranial pressure, including secondary intracranial hypertension. Headache with eye/visual symptoms and weakness needs assessment for papilledema and imaging.
• Demyelinating disease, for example multiple sclerosis, particularly if neurologic deficits have occurred in episodes or there are visual symptoms, numbness, imbalance, or bladder changes.
• Seizure with postictal weakness (Todd paralysis) if there was any unexplained episode of altered awareness, jerking, confusion, or a period of weakness after waking.

2. Cervical spine or peripheral nerve causes

• Cervical radiculopathy, such as a C8 nerve-root problem from disc herniation, which may produce intrinsic hand weakness.
• Cervical myelopathy/spinal cord compression, especially if there is clumsiness in both hands, gait change, leg symptoms, urinary symptoms, or hyperreflexia.
• Ulnar, median, or radial neuropathy, brachial plexus injury, or repetitive-compression neuropathy.

3. Primary headache or eye-related disorders

• Migraine with aura, including motor or hemiplegic migraine. A first episode of motor weakness should not be labeled migraine before urgent assessment.
• Tension-type or cervicogenic headache, potentially associated with stress, poor sleep, and neck muscle tension.
• Cluster headache or another trigeminal autonomic headache, if attacks are severe and unilateral with tearing, red eye, nasal congestion, or restlessness.
• Optic neuritis, acute glaucoma, uveitis, or other ocular causes, especially if there is reduced vision, altered color vision, red eye, halos, or pain on moving the eye.

4. Endocrine, metabolic, and systemic causes

• Hyperthyroidism/thyrotoxicosis: can cause anxiety, pacing/restlessness, palpitations, insomnia, tremor, heat intolerance, and marked weight loss. It does not by itself safely explain new focal hand weakness.
• Diabetes mellitus, particularly if there is thirst, frequent urination, fatigue, or blurry vision.
• Adrenal insufficiency, if there is dizziness on standing, abdominal symptoms, salt craving, skin darkening, or profound fatigue.
• Anemia, vitamin B12 deficiency, electrolyte disturbance, or other metabolic disorders.
• Infection or inflammatory disease, including HIV or tuberculosis depending on risk factors and associated symptoms such as fever, night sweats, lymph nodes, cough, diarrhea, or rash.
• Malignancy is less common at age 23 but unintentional rapid weight loss needs evaluation.
• Carbon monoxide exposure, particularly if headaches occur at home or others in the household have headaches, nausea, dizziness, or fatigue.

5. Cardiac, gastrointestinal, substance-related, and psychiatric contributors

• Panic attacks, generalized anxiety, PTSD, or trauma-related hyperarousal can cause racing heart, chest burning/tightness, pacing, insomnia, headache, reduced appetite, and weight loss.
• Major depression or an eating disorder may also cause insomnia and weight loss.
• Stimulant use, including amphetamines, cocaine, excessive caffeine, energy drinks, nicotine, ADHD medications, thyroid supplements, or some decongestants can cause palpitations, anxiety, insomnia, weight loss, headache, and raise stroke risk.
• GERD/gastritis may explain chest burning, but not focal hand weakness.
• Arrhythmia should be considered if palpitations are sustained, irregular, associated with dizziness/fainting, or occur during exertion.

Immediate assessment should include

• Full neurologic examination: face, speech, power, sensation, reflexes, coordination, gait.
• Vital signs including blood pressure, heart rate, temperature, oxygen saturation, and glucose.
• Eye examination including visual acuity, pupils, eye movements, and fundoscopy for papilledema.
• ECG and targeted blood tests: CBC, electrolytes, kidney/liver profile, glucose/HbA1c, TSH/free T4, inflammatory markers, and tests guided by the history.
• Urgent brain imaging, often CT initially if symptoms are acute, and MRI brain with vascular imaging as indicated. Cervical spine imaging may also be needed.