A young male patient who is a case of schizophrenia was started on haloperidol 5 mg. On 3rd day, he came to the hospital accompanied by his father with uprolling of both eyes. A complete neurological examination revealed no spasticity or any other abnormalities. Visual acuity was found to be normal. Most likely diagnosis is:

**Core Concept**
Haloperidol is a typical antipsychotic medication that can cause extrapyramidal side effects (EPS) due to its dopamine D2 receptor antagonism in the nigrostriatal pathway. EPS can manifest as acute dystonia, a sudden onset of involuntary muscle contractions.

**Why the Correct Answer is Right**
The patient's uprolling of both eyes, known as oculogyric crisis, is a type of acute dystonia. This condition occurs when haloperidol blocks dopamine D2 receptors in the brainstem, leading to an imbalance in neurotransmitter activity. The nigrostriatal pathway, which involves the substantia nigra and the caudate nucleus, is responsible for coordinating voluntary movements. By blocking dopamine receptors in this pathway, haloperidol can cause abnormal movements, such as oculogyric crisis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the patient's symptoms do not match a seizure disorder, which would typically involve loss of consciousness, convulsions, or other neurological abnormalities.
**Option B:** This option is incorrect because the patient's visual acuity is normal, ruling out a diagnosis of optic neuritis or other visual pathway disorders.
**Option C:** This option is incorrect because the patient's symptoms do not match a diagnosis of schizophrenia, which is already known and not the focus of the question.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that antipsychotic medications like haloperidol can cause EPS, including acute dystonia, especially in young males. This knowledge can help clinicians adjust medication doses or switch to alternative medications to minimize the risk of EPS.

**Correct Answer: C. Acute dystonia. Oculogyric crisis is a type of acute dystonia.**

✓ Correct Answer: A. Acute dystonia