Early in the morning, Zhaxi arrived at the Institute as usual at six. He sat in the demonstration room, opened his notebook, and prepared to continue organizing the materials for Professor Zhou’s case when his phone rang.

It was Professor Yang. 𝙛𝓻𝒆𝓮𝒘𝙚𝙗𝒏𝙤𝙫𝓮𝒍.𝓬𝒐𝙢

"Come to my office." The voice on the other end was calm, no different from usual.

Professor Yang so early today!

Zhaxi closed his notebook and walked quickly to Professor Yang’s office. The door to Yang Ping’s office was open, and he was standing in front of the whiteboard, but he was not looking at the clues for Professor Zhou’s case. The whiteboard had been wiped clean, with new things written on it.

"Sit!" Yang Ping pointed to a chair, sat down opposite, and placed a printed medical record on the table.

Zhaxi glanced at the cover of the medical record—it was a patient from the Neurology Department of Sanbo Hospital. He looked up at Yang Ping, a bit puzzled.

Yang Ping seemed to read his mind and said, "This patient, the Neurology Department can’t handle it and has requested a hospital-wide consultation. I looked at the information and found it interesting. You’re going to follow this consultation."

Zhaxi was taken aback: "Me?"

Yang Ping nodded: "Yes, you follow it, from taking the medical history, physical examination, ordering tests, reviewing the literature, analyzing the diagnosis, to formulating a treatment plan—it’s all up to you. I’ll be watching from the side but won’t help you unless you make a deadly mistake."

Zhaxi opened his mouth, wanting to say something, but Yang Ping had already pushed the medical record in front of him.

"From Professor Zhou’s case, you’ve learned one thing—how to find the critical chain of evidence from a pile of seemingly unrelated clues. Now, use this ability on patients. Solving a case and treating a patient is essentially the same thing."

"As for that case, don’t worry about it. That’s the police’s business. Our task is just to provide the necessary medical consultation."

Zhaxi took a deep breath and opened the medical record. The first page contained basic information: the patient is female, 43 years old, a local of Nandu, company employee. Main complaint: recurrent headaches and blurred vision for three months, worsening with right-sided limb weakness for a week. He continued to read, and the admission record stated that three months ago, the patient began to experience paroxysmal headaches at undetermined locations, sometimes the forehead, sometimes the occipital region, with the pain being a distending or pulsating pain, moderate in degree, and tolerable. It was accompanied by blurred vision, seeing things as if through fog. She had previously consulted at an external hospital, had a head CT scan, which showed no abnormalities. The doctor diagnosed it as a migraine and prescribed painkillers, which were ineffective. A week ago, the headache suddenly worsened, accompanied by right limb weakness, difficulty holding things steadily, and a tendency to veer to the right while walking. The external hospital rechecked the head CT, still showing no abnormalities. The patient was transferred to the Neurology Department of Sanbo Hospital.

Zhaxi turned to the next page; it was the initial examination record of the Neurology Department. Physical examination: clear consciousness, fluent speech, pupils equal and round, sensitive to light reflex, eyeball movement free, no nystagmus. Right limb muscle strength grade four less, left grade five. Right Babinski sign positive. No abnormalities in the sensory system examination. Coordination movement: right finger-nose test and heel-knee-shin test were not stable or accurate.

He frowned. This patient’s presentation is very strange—headache, blurred vision, right limb weakness, ataxia, but the head CT is normal. Normal CT indicates no obvious brain hemorrhage, brain tumor, or brain infarction. So what is it? He continued to flip through, finding a few lab reports behind. Blood routine is normal, liver and kidney function are normal, electrolytes are normal, coagulation function is normal. All routine tests are normal.

Zhaxi looked up at Yang Ping: "Professor Yang, all the tests are normal."

Yang Ping nodded: "Yes, that’s why the Neurology Department can’t handle it."

Zhaxi lowered his head again, continuing to browse through the medical records. Behind it was the record from an ophthalmology consultation requested by the Neurology Department. Ophthalmic examination: vision in the right eye 0.6, left eye 0.8, no improvement with correction. Fundus examination: both optic disc margins are blurred with mild edema. The ophthalmology diagnosis is: bilateral optic disc edema, cause to be determined.

Optic disc edema? It indicates increased intracranial pressure. But the head CT is normal, with no evidence of mass lesions. What then causes the increased intracranial pressure? He recalled a concept he learned in medical school: increased intracranial pressure with a normal CT might be caused by intracranial venous sinus thrombosis, meningitis, intracranial infection, or metabolic diseases.

Zhaxi felt amazed; ever since Professor Yang let him participate in that case, he now feels no boredom with these thick, complex medical records but instead a strange excitement, eager to find the answer.

He continued to turn the pages and found a record of a lumbar puncture. The Neurology Department performed a lumbar puncture measuring intracranial pressure at 280 mm water column, with the normal value being 80 to 180. Zhaxi’s frown deepened. Intracranial pressure was indeed elevated, and significantly so. But the routine, biochemical, and cytological examination of cerebrospinal fluid was normal. No infection, no tumor cells, no abnormalities.

He finished reading the entire medical record, leaned back on the chair, his mind in turmoil. A 43-year-old female, has been experiencing recurrent headaches and blurred vision for three months, right limb weakness, and ataxia a week ago. Increased intracranial pressure, but normal head CT, normal lumbar puncture, all routine tests normal—what disease is this?

Yang Ping sat quietly opposite him, watching without saying anything. Zhaxi knew Yang Ping was waiting for him to speak.

"Professor Yang, I need to see the patient." Zhaxi stood up.

Yang Ping nodded: "Go, I’ll wait for you in the office. Solving a case requires being on the scene. We doctors must personally contact the patient. That’s why we’re called clinical doctors."