Neurology in Question

Chapter 3

The extern nods.

“So the basilar artery isn’t born from the posterior cerebral arteries?”

“Correct. It’s the other way around.”

“And subarachnoid hemorrhage isn’t a stroke?”

“It is a form of hemorrhagic stroke. Stroke includes both ischemic and hemorrhagic events.”

The extern looks at the CT again.

“How do we confirm a subarachnoid hemorrhage if the CT is negative?”

“If clinical suspicion remains high despite a negative CT, lumbar puncture may be considered when appropriate. We look for red blood cells and xanthochromia in the cerebrospinal fluid.”

“And what are the normal CSF values?”

“Opening pressure is usually around 10 to 20 cm H₂O. Protein is approximately 15 to 45 mg/dL. Glucose is usually around 45 to 80 mg/dL, or roughly 60% of the serum glucose. The exact reference ranges can vary between laboratories.”

“And in subarachnoid hemorrhage?”

“The important findings are red blood cells and xanthochromia. The glucose level is not the main diagnostic finding.”

“Does she need surgery?”

“If this is an aneurysmal subarachnoid hemorrhage, it is a medical emergency. We stabilize the patient and identify the source of bleeding. If an aneurysm is found, it needs to be secured urgently, usually by endovascular coiling or surgical clipping.”

“And if she develops hydrocephalus?”

“Then she may need cerebrospinal fluid drainage, such as an external ventricular drain.”

The intern nods.

“Can we calculate intracranial pressure from her blood pressure?”

“No. Intracranial pressure is measured directly when monitoring is indicated. We don’t calculate it from blood pressure.”

“Then how do we calculate cerebral perfusion pressure?”

“CPP equals MAP minus ICP.”

“And MAP?”

“Approximately systolic blood pressure plus twice the diastolic blood pressure, divided by three.”

The intern writes it down.

“Understood.”

I look at the patient.

“Let’s treat this emergency.”

The next patient arrives.

A man with a known peanut allergy has eaten a cake containing peanuts.

His face is swollen.

Then he suddenly faints.

“His blood pressure is 80/50.”

“He’s in anaphylactic shock.”

His SpO₂ is 93%.

“Treat him immediately.”

“Should we give antihistamines?”

“They can help with some allergic symptoms, but they are not the first-line treatment for anaphylaxis.”

I prepare the emergency treatment.

“Give intramuscular adrenaline immediately.”

An intern looks at me.

“Why adrenaline? He isn’t in cardiac arrest.”

“Because adrenaline is the first-line treatment for anaphylaxis. Cardiac arrest is not required.”

The nurse checks his vital signs.

“Should we perform an ECG?”

“Yes. Monitor him continuously. He’s in shock.”

Another intern looks at the laboratory results.

“His IgE is elevated.”

“That doesn’t change the acute treatment. Anaphylaxis is diagnosed clinically. We don’t wait for an IgE result before giving adrenaline.”

Oxygen is administered.

Intravenous fluids are started.

His blood pressure gradually improves.

“His SpO₂ is 96%.”

“Good. Continue monitoring him.”

His facial swelling begins to decrease.

“The emergency is under control.”

The patient takes a deep breath.

“I was supposed to come here because of my sleep apnea.”

I look at him.

“You’re already using CPAP?”

“Yes.”

“CPAP is a common treatment for obstructive sleep apnea. It maintains positive airway pressure and prevents repeated collapse of the upper airway during sleep.”

“What is the humidifier for?”

“It adds moisture to the air and can reduce dryness caused by the device.”

“How do you grade sleep apnea?”

“We use the apnea-hypopnea index, or AHI. In adults, an AHI below 5 is generally considered normal. Five to less than 15 is mild, 15 to less than 30 is moderate, and 30 or more is severe.”

“Is CPAP only used when the patient refuses an oral appliance?”

“No. CPAP can be first-line treatment, especially for moderate or severe obstructive sleep apnea. An oral appliance is an alternative for selected patients.”

“And obstructive sleep apnea is caused by the central nervous system?”

“No. In obstructive sleep apnea, the upper airway repeatedly collapses or becomes obstructed during sleep despite continued respiratory effort. That’s different from central sleep apnea, where respiratory effort itself is absent.”

The patient nods.

“Understood.”

The next patient is 70 years old.

He cannot see through his left eye.

He also has decreased hearing on the left side and drooping of the left side of his face.

“Does he have Bell’s palsy?” an intern asks.

“No.”

“Why?”

“Bell’s palsy is an isolated peripheral facial nerve palsy. It can explain facial weakness, but it doesn’t explain his visual loss and hearing loss.”

I point toward the patient.

“His visual loss suggests involvement of the optic pathway. His hearing loss suggests involvement of the auditory pathway, and his facial drooping suggests involvement of the facial nerve.”

“So it’s a tumor?”

“Multiple cranial nerve deficits should make us think about a structural lesion, including a skull-base lesion or tumor. We need to localize it first.”

“An optic neuroma?”

“Not necessarily. ‘Optic neuroma’ is not a diagnosis we can make from these findings alone. We need imaging.”

“Can we biopsy the optic nerve?”

“No. We don’t biopsy the optic nerve simply to establish this diagnosis. MRI with contrast is more appropriate for evaluating the lesion.”

Mira enters with the MRI report.

“MRI shows a large mass with restricted diffusion.”

“Restricted diffusion can occur in several conditions. It does not automatically prove that the lesion is a tumor. What does the rest of the imaging show?”

“It is a large skull-base mass.”

“We need to determine its exact location and obtain a tissue diagnosis if appropriate.”

The CT scan of the chest, abdomen, and pelvis is performed.

Mira looks at the images.

“It shows an abdominal mass and a pelvic mass.”

“Those could represent additional lesions, but we need to determine whether they are metastases. We need a tissue diagnosis and appropriate staging.”

“Can I call it T4N0M1?”

“Only if the specific cancer’s staging system defines the primary tumor as T4 and the distant lesion as M1. TNM staging is cancer-specific. There is no universal formula where we multiply T by two and add N.”

“So stage IV?”

“If those lesions are confirmed to be distant metastases, the disease would generally be considered metastatic and may correspond to stage IV in many cancers. But the exact stage depends on the cancer type and its staging system.”

“What treatment do we give?”

“First, we need the pathology and molecular profile. Then we can decide on treatment.”

“Radiochemotherapy and targeted therapy?”

“Possibly, depending on the tumor. We cannot choose the treatment before knowing exactly what we are treating.”

The patient looks worried.

“Does that mean I can’t have surgery?”

“Not necessarily. Metastatic disease can make surgery inappropriate in some situations, but it does not automatically mean surgery is impossible. It depends on the primary tumor, the metastases, resectability, symptoms, and your general condition.”

The patient is transferred to oncology.

The oncologist returns with the biopsy results.

“We have the histology and molecular profile.”

“Now we can choose the treatment.”

The oncologist explains the treatment plan.

“Cyclophosphamide may be used as part of certain chemotherapy regimens, but it is not a universal treatment for every cancer.”

“And radiotherapy?”

“Radiotherapy can be delivered using techniques such as IMRT. The schedule depends on the tumor and treatment plan. It is usually delivered in multiple fractions.”

“And targeted therapy?”

“That depends on the tumor and its molecular characteristics. Bevacizumab, for example, is a targeted anti-VEGF therapy used in certain cancers.”

“And pembrolizumab?”

“Pembrolizumab is an immunotherapy. It is a PD-1 inhibitor.”

“How often do I receive these treatments?”

“There is no single schedule. Chemotherapy is usually given in cycles, depending on the regimen. Some targeted therapies are administered every few weeks. Radiotherapy is divided into a planned number of fractions.”

“What tests do I need before treatment?”

“We check your blood count, kidney function, liver function, and other tests according to the treatment. Before bevacizumab, we pay particular attention to blood pressure and urine protein. Before radiotherapy, imaging and treatment planning are required.”

The treatment begins.

Weeks pass.

The patient’s condition stabilizes after completing the planned treatment.

He touches his hair.

“I guess I’ll have to watch my hair fall.”

He looks at Dr. John.

“Will it grow back? My aunt’s hair hasn’t grown back, and it’s been five years since she was diagnosed with cancer and treated.”

“Chemotherapy-related hair loss usually improves after treatment, but the timing and completeness of regrowth depend on the drugs and doses. Some patients can have persistent or altered hair growth.”

“So it may come back?”

“Usually, yes. But you’ll have to be patient.”

Dr. John smiles bitterly.

The next patient arrives.

A 23-year-old man is brought to the neurosurgery emergency department by his father.

He’s unconscious.

His heart rate is 100 beats per minute.

SpO₂ is 100%.

Blood pressure is 100/60 mmHg.

Temperature is 39°C.

He has coarse crackles on auscultation.

“He has a fever and crackles. We need to investigate pneumonia.”

A chest radiograph is performed.

It shows bilateral upper-lobe air-space opacities.

“The lungs are affected in both upper lobes.”

“Is this automatically a complicated pneumonia?”

“No. Bilateral pneumonia can be serious, but complicated pneumonia usually refers to complications such as parapneumonic effusion, empyema, necrosis, or abscess.”

“We’ll do a CBC, blood cultures, and a pneumococcal urinary antigen.”

The results arrive.

“CBC is normal.”

“Blood cultures are negative.”

“Pneumococcal urinary antigen is positive.”

“So pneumococcal pneumonia is supported.”

“Give him the appropriate antibiotic therapy.”

The nurse administers the prescribed treatment.

His temperature decreases to 37°C.

“He is now afebrile.”

“Good. Continue monitoring him.”

But the patient hasn’t regained consciousness.

“What do we do now?” the panicked nurse asks.

“We need to investigate the altered consciousness. Perform an urgent brain scan.”

The CT scan is performed.

It shows diffuse cerebral edema with compressed ventricles.

“The ventricles are smaller.”

“That does not suggest hydrocephalus. Hydrocephalus usually causes ventricular enlargement.”

“Then what is causing the loss of consciousness?”

“Severe cerebral edema can increase intracranial pressure and impair consciousness.”

I look at the patient.

“We need urgent neurological and neurosurgical management.”

“Can we perform a lumbar puncture?”

“No. Significant cerebral edema and mass effect can increase the risk of brain herniation, so lumbar puncture may be dangerous.”

Arthur looks at the monitor.

“MAP is approximately 73 mmHg.”

“Correct. MAP is approximately (100 + 2 × 60) divided by 3, which is about 73 mmHg.”

“And the ICP?”

“We cannot calculate ICP from the blood pressure. If an exact ICP measurement is required, it must be obtained through intracranial monitoring.”

“Then how do we calculate CPP?”

“CPP equals MAP minus ICP.”

The patient is treated for the cerebral edema and its underlying cause.

His consciousness gradually returns.

His father looks at us.

“You saved his life.”

Arthur looks at me.

“What treatment do we give for adult hydrocephalus?”

“First, determine the cause. Hydrocephalus can require CSF diversion, such as an external ventricular drain, endoscopic third ventriculostomy, or a ventriculoperitoneal shunt, depending on the situation.”

“How is adult hydrocephalus different from childhood hydrocephalus?”

“In infants, the skull can expand because the sutures and fontanelles are not completely fused. Hydrocephalus can therefore cause increasing head circumference and a bulging fontanelle. In adults, the skull is rigid, so increasing intracranial volume can lead to raised intracranial pressure.”

“How do we differentiate cerebral atrophy from hydrocephalus?”

“In cerebral atrophy, the ventricles enlarge because brain tissue has been lost, and the cortical sulci usually enlarge as well. In hydrocephalus, the ventricles are enlarged out of proportion to the sulci. Other imaging signs help determine the cause.”

“Is scaphocephaly caused by hydrocephalus?”

“No. Scaphocephaly usually results from premature fusion of the sagittal suture. Hydrocephalus can enlarge the skull in infants, but it does not cause sagittal craniosynostosis.”

“A baby comes with Apert syndrome. What happens to the skull?”

“Apert syndrome is associated with craniosynostosis, particularly premature fusion of the coronal sutures. It is also associated with midface hypoplasia and syndactyly.”

“So it’s not mainly the lambdoid suture?”

“Correct.”

The next patient comes to me.

His eyes move rapidly up and down.

“It’s nystagmus.”

“I was diagnosed with a meningioma. Then my eyes began moving on their own. What’s wrong with me?”

“It’s nystagmus. Your tumor may be responsible if it affects the brainstem, cerebellum, or vestibular pathways. We need to know its exact location.”

“Will it stop after I’m cured of the tumor?”

“It may improve if the tumor is responsible and is successfully treated, but I can’t guarantee that it will disappear completely.”

The MRI is reviewed.

“Your tumor is 4.5 cm.”

“What’s the stage?”

“We cannot determine a TNM stage without knowing the tumor type. Meningiomas are generally not staged using the same TNM system used for many cancers.”

“What about treatment?”

“We’ll determine it according to the tumor’s location, grade, symptoms, growth, and resectability.”

"And if it were metastatic cancer?”

“Then treatment could include surgery, radiotherapy, chemotherapy, targeted therapy, or immunotherapy, depending on the pathology and molecular profile.”

The patient nods.