1. Answer B. (MN-110) Cortical atrophy associated with cognitive aging disorders results in hydrocephalus ex vacuo with an otherwise normal intracranial pressure, cerebrospinal fluid (CSF) production, flow, and reabsorption. Choroid plexus papilloma is the only known cause of hydrocephalus to oversecretion of CSF. Obstructive hydrocephalus describes conditions that result in near complete blockage of CSF flow within the ventricular system, such as acute intraventricular hemorrhage or a third ventricular colloid cyst, among other causes. Aside from normal pressure hydrocephalus, causes of communicating hydrocephalus often involve some degree of poor reabsorption of CSF due to blockage of the arachnoid villi (post-inflammatory or post-hemorrhagic) or occlusion of cerebral veins. Tuberculous meningitis and subarachnoid hemorrhage also impair the absorptive capacity due to inflammation in setting of infection and/or bleeding.

2. Answer E. (MN-110) The patient has acute obstructive hydrocephalus from an intraventricular mass and is rapidly decompensating. In addition to basic resuscitation of ABC’s, this is a neurosurgical emergency and this patient needs immediate intervention. Placement of an EVD is the most appropriate next step, which will immediately divert CSF flow and reduce intracranial pressure. VPS placement is not typically performed in an emergent fashion, and LD placement is dangerous in this setting as it could cause downward brain herniation. Steroids are unlikely to be helpful if vasogenic edema is not the primary cause of obstruction and will take many hours to take effect. The patient will later need an MRI brain for better characterization of the mass; however, this is lower priority and the CT provides adequate information for immediate patient care.

3. Answer B. (MN-110) Macewen sign, named for Sir William Macewen (1848-1924), a surgeon in Glasgow, Scotland, is a clinical sign to detect hydrocephalus and brain abscess. Percussion (tapping the middle finger) on the skull at a particular spot (near the junction of the frontal, temporal, and parietal bones) yields an unusually resonant sound in the presence of hydrocephalus or a brain abscess. Collier sign is bilateral or unilateral eyelid retraction and is an accepted medical sign of a midbrain lesion. McConnell sign is regional RV dysfunction with akinesia of the mid free wall but normal motion at the apex; it is a distinct echocardiographic finding described in patients with acute pulmonary embolism. Murphy sign, indicative of acute cholecystitis, is tested for during an abdominal examination and is performed by asking the patient to breathe out and then gently placing the hand below the costal margin on the right upper quadrant (the approximate location of the gallbladder).

4. Answer C. (MN-110) Gait change, described as magnetic gait, is usually the first symptom, as well as the most frequent symptom, of NPH. The clinical finding is more accurately an axial apraxia with the most obvious clinical changes being gait. The presumed anatomic basis is involvement of bilateral paramedian prefrontal and primary cortical and adjacent subcortical regions due to hydrocephalus. This change may be subacute, fluctuating, or more chronic but most often worsens over weeks or months. In addition, axial rigidity from extrapyramidal dysfunction, dementia, and urinary incontinence typically occur. The Argyll-Robertson pupil is usually seen in tertiary syphilis, not NPH.

5. Answer B. (MN-111) Interstitial edema results from bulk flow of water into the periventricular extracellular fluid compartment in patients with hydrocephalus. Osmotic edema results from acute reductions in serum osmolality, as occurs with treatment of diabetic ketoacidosis or dialysis. The inciting cause of cytotoxic edema is intracellular sodium accumulation due to energy failure and ATP depletion. Ionic edema refers to an intermediate phase of cytotoxic edema in which sodium and other ions accumulate within the extracellular space. A key component of vasogenic edema involves blood-brain barrier disruption.

6. Answer D. (MN-111) Mannitol and hypertonic saline boluses can continue to be effective even if osmolality exceeds 320 mOsm/L, at the expense of further increases in osmolality. Parenchymal ICP monitors can be used to monitor ICP in patients without ventriculomegaly. CPP should be optimized between 60 and 100 mm Hg in most patients. Sedation is a cornerstone intervention for ICP but should be interrupted for neurological assessments even if ICP is an issue. Hypertonic saline and mannitol can be used in the same patient.

7. Answer A. (MN-111) The head of bed should be elevated to 30° to improve venous drainage and reduce ICP. The other choices are all ICP reduction tools; however, they are being used incorrectly. Hypertonic saline, 23%, should be administered as a rapid infusion over 2 to 5 minutes. Mannitol should also be given as a rapid infusion (wide open) or at a pump rate of 999 mL/h. Only isotonic crystalloids should be used; hypotonic fluids such as half-normal saline should be avoided since free water will flow down its osmotic gradient into the injured brain. Excessive hyperventilation in the acute phase of TBI should be avoided; the preferred target is mild hypocapnia at 30 to 35 mm Hg.

8. Answer B. (MN-111) In the RESCUE ICP trial craniectomy resulted in a mortality reduction from 47% to 24% compared with continued medical therapy including escalation to pentobarbital coma. In the Eurotherm3235 trial hypothermia to 32 °C resulted in increased mortality, as did high-dose methylprednisolone infusion in the CRASH trial. Slit ventricles makes ventricular drain placement difficult, and at this late stage CSF drainage is not as likely as craniectomy to reduce mortality.

9. Answer C. (MN-111) Determining whether vision is threatened is the primary criterion for identifying candidates for CSF diversion in patients with IIH. IIH by definition does not cause mental status or gait abnormalities; if either are present, another diagnosis should be sought. Phase-contrast MRI shows reduced mean peak CSF flow rates compared with normal controls, but this test is not used to identify candidates for shunting, nor is endocrine evaluation.