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Idiopathic intracranial hypertension



Keywords


Idiopathic intracranial hypertension (IIH), lumbar puncture, visual obscurations


Idiopathic intracranial hypertension (IIH) is a disorder of unknown etiology, which is characterized by increased intracranial pressure (ICP). Other names have included benign intracranial hypertension and pseudotumor cerebri. The syndrome of IIH is characterized by clinical signs and symptoms of increased ICP but no evidence of intracranial mass, infection, hydrocephalus, or other apparent structural central nervous system pathology on neuroimaging studies and cerebrospinal fluid (CSF) examination.


Epidemiology


It is most common in obese women of childbearing age, and is more common in hypertensives and during pregnancy. The annual incidence has been estimated to be 3/100,000.


Clinical presentation


Symptoms include headache (84%), transient visual obscurations (69%), pulsatile tinnitus (52%), dizziness (51%), nausea/vomiting, photophobia (48%), neck pain (42%), or diplopia (24%).


Signs include papilledema, cranial nerve (CN) VI palsy, and visual disturbances: contrast sensitivity deficits, color vision loss, constricted visual fields, abnormal automated perimetry, contrast sensitivity defects, and abnormal visual acuity. Blind spot enlargement is characteristic.


Etiology


Idiopathic by definition


Other causes of generalized intracranial hypertension that are not idiopathic include venous sinus thrombosis, endocrinopathies, hyper/hypovitaminosis A, anemia, recent use of certain medications (tetracycline, indomethacin, nalidixic acid, nitrofurantoin, oral contraceptives, lithium), and prolonged use of corticosteroids. Other systemic conditions that mimic aspects of IIH include sleep apnea, pre-eclampsia, chronic obstructive pulmonary disease, right-sided heart failure, uremia, renal failure, systemic lupus erythematosus (SLE), coagulation disorders and hyperthyroidism.


Diagnosis



  1. I. If symptoms (of increased ICP) present, they may only reflect those of generalized intracranial hypertension or papilledema.
  2. II. If signs (of increased ICP) present, they may only reflect those of generalized intracranial hypertension or papilledema.
  3. III. Documented elevated ICP (> 250 mm H2O) measured in the lateral decubitus position (for adults).
  4. IV. Normal CSF composition.
  5. V. No evidence of hydrocephalus, mass, structural, or vascular lesion on magnetic resonance imaging (MRI) or contrast-enhanced computed tomography for typical patients, and MRI and magnetic resonance venography for all others.
  6. VI. No other cause of intracranial hypertension is identified. Other radiologic findings, which are not part of the formal criteria, include flattening of the posterior aspect of the globe, empty sella, distention of the perioptic nerve sheath, and transverse venous sinus stenosis.

Management



  1. I. Baseline and follow-up neuro-ophthalmologic evaluation includes visual field perimetry, optic disk stereophotographs, visual acuity, and contrast sensitivity testing.
  2. II. In patients with IIH and mild visual loss, the use of acetazolamide (up to a maximum of 4 g/day) with a low-sodium weight-reduction diet compared with diet alone resulted in modest improvement in visual field function. Although usually well tolerated, side effects include metabolic alkalosis, paresthesias of the extremities, liver dysfunction, and allergic reactions. Other medications, such as topiramate or furosemide, may be used.
  3. III. Weight loss is an essential component of management.
  4. IV. Repeated high-volume lumbar punctures may provide relief, and in some cases remission, though this remains controversial.
  5. V. Optic nerve sheath fenestration, venous sinus stenting, ventriculoperitoneal shunting in cases with rapidly progressing visual loss or intractable headaches.
  6. VI. Steroids provide symptomatic relief, but the myriad side effects make these drugs undesirable for chronic treatment.


Immunization, vaccination



Keywords


Vaccines, adverse events, reactions, Guillain-Barré, ADEM, subacute sclerosing panencephalitis, SSPE, seizures


Many neurologic symptoms are blamed on antecedent immunizations, but it is difficult to evaluate true causality. A common concern is when patients hear about small studies suggesting causal relationships between a vaccination and a particular disease. Studies and vaccine modification (such as the acellular pertussis vaccine) are ongoing to minimize risk to patients.


Vaccines against the following diseases and infections are currently available:



  1. I. Anthrax: Recent studies among immunized military personnel have shown no increase in disability among those receiving the vaccine.
  2. II. Japanese encephalitis: Acute disseminated encephalomyelitis (ADEM) has been reported to occur after vaccination. Actual incidence is unclear, as several studies show wildly different rates, ranging from 0 cases in 813,000 vaccinations to 1 in 600. Two studies showed incidence rates between 0.2 and 2 in 100,000.
  3. III. Haemophilus influenzae type B: no complications have been reported.
  4. IV. Hepatitis B: There has been public concern about increased risk of MS, but this was disproved in a large study.
  5. V. Influenza: There may an increased frequency of Guillain-Barré syndrome (GBS) following influenza vaccination. Incidence of giant cell arteritis may also be increased.
  6. VI. Measles: This vaccine is ordinarily combined with mumps and rubella (MMR) vaccines. Except for febrile seizures in children who are genetically predisposed, neurologic complications are uncommon but controversial. There are case reports of ADEM after measles vaccine, but that risk is very minor compared to the substantially higher risk of ADEM and subacute sclerosing panencephalitis from natural measles. In a very large study, MMR vaccine was shown to have no increase in risk of neurologic complications. A 1998 paper by Wakefield that gave rise to the belief that the MMR vaccine might be associated with increased rates of autism has been discredited and has been retracted by the Lancet.
  7. VII. Meningococcus: There was concern for increased incidence of GBS after receiving the Menactra formulation, but two large safety trials were unable to reproduce this risk.
  8. VIII. Pertussis: The new, acellular pertussis vaccine (diphtheria and tetanus toxoids and pertussis—DTaP) has replaced the diphtheria, tetanus toxoid, and pertussis (DTP) vaccine after many concerns about increased neurologic complications. These complications appear to be much less frequent with the new vaccine. Simple febrile seizures, with no long-term effects, can occur within 24 hours of administration. Autism, epilepsy, and hypotonic/hyporesponsive episodes, all previously related to the DTP vaccine, are much less common now.
  9. IX. Pneumococcus conjugate: There is a small increase in the frequency of seizures, usually febrile, in children.
  10. X. Poliomyelitis: Paralytic poliomyelitis is the only known complication of oral polio vaccine (OPV). It is especially a concern for immunodeficient contacts. The inactivated polio vaccine (IPV) is now replacing it in most countries to reduce this risk.
  11. XI. Rabies: Whole-virus vaccines that contain myelin basic protein are associated with ADEM and polyneuritis within 2 weeks after immunization.
  12. XII. Rubella: Transient arthralgias may develop in up to 40% of patients. No causal evidence exists for association with polyneuritis or other neuropathies.
  13. XIII. Toxoids: These vaccines contain antigens from toxins, not from the microbes themselves. Tetanus and diphtheria are the most common and are often given together. Allergic hypersensitivity is the most common (though rare) complication. Demyelinating neuropathy with complete recovery has also been reported.
  14. XIV. Smallpox: Severe, usually transient headaches are common after vaccination.
  15. XV. Varicella: There have not been any serious neurologic complications. The theoretic concern of a shift to more serious adult zoster infections as childhood immunization wanes will be tested in the years to come.
  16. XVI. Human papilloma virus: most common events include headache, nausea, dizziness, and syncope. Rare case reports implicate GBS and ADEM.
  17. XVII. Other agents: Chemical vehicles, preservatives, and contamination have caused complications. Aluminum, commonly in diphtheria, tetanus, and hepatitis A and B vaccines, rarely causes a myofascitis. Mercury was used until 1999 in several preparations. Bovine products carry the risk of prion diseases but have been well monitored in the United States.


References


Markovitz L.E., et al. Human papillomavirus vaccination: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2014;63:1–30.


Yih W.K., et al. No risk of Guillain-Barré syndrome found after meningococcal conjugate vaccination in two large cohort studies. Pharmacoepidemiol Drug Saf. 2012;21:1359–1360.



Intracranial pressure



Keywords


Increased intracranial pressure, Monroe-Kellie doctrine, cerebral perfusion pressure, acute management of increased intracranial pressure, intracranial hypotension


Basic concepts


Normal values of intracranial pressure (ICP) range from 5 to 15 mm Hg (torr), which equals 65 to 200 mm cerebrospinal fluid (CSF) or H2O (conversion: 1 torr = 13.6 mm H2O). Factors that determine the level of ICP are the volume of intracranial contents and arterial and venous pressures. After the cranial sutures fuse, the skull becomes an inelastic, closed container with a fixed total intracranial volume consisting of 3 components: brain, CSF, and blood. The Monroe-Kellie doctrine states that the sum of intracranial brain tissue, CSF, and blood volumes is constant; therefore, an increase in the volume of one must be compensated by an equal decrease in another compartment. Slow increases in the volume of one compartment can be compensated by decreases in the others, but a rapid rise in ICP is not well tolerated and increases the risk of herniation or the occurrence of global ischemia and is a neurologic emergency. Cerebral perfusion pressure (CPP) is critical to maintain adequate cerebral blood flow (CBF) and is calculated as a difference between mean arterial pressure (MAP) and ICP (CPP = MAP-ICP). CPP less than 50 mm Hg is detrimental to brain function and survival. Following any major cerebral injury, ICP should be maintained as close to normal as possible, to provide a margin of safety. Continuous ICP monitoring provides useful information about “pressure waves” and may be used to guide treatment. Plateau waves, consisting of episodic surges in ICP (sometimes exceeding 450 mm H2O) can occur several times an hour, especially with pain and iatrogenic maneuvers, such as suctioning, and are associated with increased risk of herniation.


Clinical presentation of increased ICP depends on the underlying process, compartmentalized or diffuse, and whether it is acute or chronic. Manifestations of headache, papilledema, diplopia, or focal signs may occur. Cushing’s triad of bradycardia, hypertension, and slowing of respiration may occur in patients with significant increased ICP and as such these patients will additionally have a depressed level of consciousness. If there is an element of brainstem compression or involvement of the right insula, patients may develop cardiac arrhythmias, such as atrial fibrillation, nodal and ventricular bradycardia, large T waves, prolonged QT intervals, and changes in ST segments.


Causes of increased intracranial pressure


Space-occupying lesions, cerebral edema (cytotoxic edema secondary to brain infarction or vasogenic edema commonly caused by tumor), trauma, intra/extra-axial hemorrhages (hemorrhagic stroke, subarachnoid hemorrhage, subdural hematoma, epidural hematoma), infections, venous sinus thrombosis, and pseudotumor cerebri may increase ICP. An acute rise in blood pressure beyond the autoregulatory curve causes an elevated ICP, as seen in hypertensive encephalopathy; chronic hypertension does not cause a change in ICP. Processes that increase venous pressures cause increases in ICP and include jugular compression (as reflected by Queckenstedt’s test during LP), superior vena cava obstruction, congestive heart failure (CHF), or Valsalva maneuvers. Postural effects alter the pressures in the intracranial venous sinuses, which in turn alter the CSF pressure.


Treatment



  1. I. General measures: Patients with clinical evidence of increased ICP can benefit from a few simple interventions. The most critical first step is ensuring adequate cardiopulmonary support, starting with assessment of the patient’s airway, breathing, and circulation. Patients with a depressed mental status, indicated by a Glasgow Coma Scale score of less than 8, should be intubated and supported with mechanical ventilation. Elevate the head to 30 to 45 degrees above horizontal with the neck in a straight position to optimize the jugular venous drainage; equalize fluid balance, control fever (hyperthermia markedly increases CBF as a reflection of increased cerebral energy metabolism), and avoid hypotonic IV solutions. Avoid hypotension (SBP < 90 mm Hg); aim for a CPP above 60 mm Hg. If BP control is necessary, use beta blockers and calcium channel blockers, avoiding antihypertensives with known effect of increasing ICP: nitroprusside or nitropaste. Avoid hypoxia (Po2 < 60 mm Hg) and ventilate to normocarbia (Pco2 35–40 mm Hg). All patients with clinical concern for increased ICP require emergent neuroimaging once their airway is protected and they are hemodynamically stable. A non-contrasted CT scan is a reasonable initial approach to identify the underlying pathological process to quickly determine if there is a role for neurosurgical intervention. Depending on the results of the CT brain scan, it may be appropriate for the neurosurgeon or neurointensivist to introduce an external ventricular drain (EVD) for treatment of obstructive hydrocephalus. Furthermore, an EVD provides the ability for continuous ICP monitoring as well as therapeutically draining the CSF.
  2. II. Active measures:

    1. A. Hyperventilation can be used as a temporary and rapid intervention for lowering ICP. Hypocarbia results in cerebral vasoconstriction and rapidly decreases ICP. The Pco2 should be maintained between 30 and 35 mm Hg while additional therapies are considered. Prolonged hyperventilation is not effective.
    2. B. Mannitol is given as a 20% IV solution, 0.5 to 1 g/kg over 15 minutes, and repeated at 3- to 6-hour intervals, and can be infused through a peripheral IV line. Mannitol is best used when ICP can be directly monitored; otherwise, it should be titrated to produce a serum osmolality of 320 to 340 osmol/L. Urine output should be monitored. While using mannitol, clinicians must look out for electrolyte depletion such as hypokalemia, pseudohyponatremia, volume depletion causing hypotension, and causing volume overload in CHF or end-stage renal patients. Volume depletion can be addressed by 1/1 cc urine output/normal saline replacement. Mannitol may be used in end-stage renal patients who can be dialyzed.
    3. C. Many centers have moved toward using hypertonic saline infusions as the hyperosmolar therapy of choice. Hypertonic saline can be temporarily infused through a peripheral line at 2% while central access is obtained. A bolus dose of 23.4% saline can be given through a central line, followed by continuous 3% infusion with frequent draws of serum sodium levels every 4 to 6 hours while the rate of infusion is being determined. Goal sodium is 155 to 160. Patients will typically benefit from hyperosmolar therapy for 3 days, after which point the therapy should be weaned to permit the levels to drift back to normonatremia. Do not rapidly correct the hypernatremia as this may precipitate central pontine myelinolysis.
    4. D. Glucocorticoids are used in controlling brain edema associated with brain tumors and meningitis. Dexamethasone 0.15 mg/kg every 6 hours for 2 to 4 days should be started 10 to 20 minutes prior to or along with the first dose of antibiotics when treating bacterial meningitis in an adult. Vasogenic edema in the setting of a brain tumor should be treated acutely with 8 mg of dexamethasone q 8 hours for a total of 24 mg per 24 hours. Pending neurosurgical or radiation options, this high dose should be maintained on a short-term basis, with weaning of the dose over days to a more typical 4 to 6 mg BID.
    5. E. Hypothermia (32 to 34°C) can lower ICP. However, several randomized control trials have failed to demonstrate clinical benefit.
    6. F. Neuromuscular blockade may be necessary, using short-acting agents such as cisatracurium.
    7. G. Barbiturate coma with burst suppression can decrease ICP and is a last resort medical therapy; complications include further sedation of comatose patients, hypotension often requiring vasopressors to maintain blood pressure, and sepsis. Pentobarbital may be given at 10 mg/kg IV bolus and then 5 mg IV/kg/hr titrate to 2 to 5 bursts per minute.

  3. III. Surgical evacuation when possible offers rapid and definitive relief of intracranial hypertension. Although intraparenchymal, epidural, subdural, and subarachnoid ICP monitors can be used, the intraventricular catheter is the most accurate and allows therapeutic CSF EVD. EVD results in immediate ICP reduction, especially in cases with hydrocephalus. Indications for EVD include severe brain insult with Glasgow Coma Scale score less than 8 and an abnormal head CT. EVD is indicated, even with a normal CT, when additional factors are present, such as age over 40 years, SBP below 90 mm Hg, and decerebrate or decorticate posturing. Hemicraniectomy has been used after massive middle cerebral stroke and appears to be promising.

Intracranial hypotension


Decreased ICP may occur in the setting of CSF leakage, either spontaneously through openings in the dura to sinuses or mastoid, after lumbar puncture or neurosurgery, or through overshunting. Postural headache, similar to that observed after lumbar puncture, is a frequent symptom. Diagnosis is confirmed by demonstration of CSF leak on cisternogram or other evidence of CSF leak (positive glucose test in pharyngeal secretions). MRI may show meningeal enhancement. Spontaneous remission may occur, and treatment depends on the cause; occasionally dural graft may be necessary.



Intracranial Stenosis



Keywords


Intracranial arterial stenosis, WASID, stenting, aspirin, warfarin



  1. I. Epidemiology. Intracranial artery stenosis (ICS) secondary to atherosclerosis is a significant cause of ischemic stroke, accounting for 5% to 10% of all ischemic strokes. The annual risk of stroke in patients with ICS is estimated at 3% to 15%, although the warfarin versus aspirin for intracranial disease (WASID) trial showed a risk of recurrent vascular events at 15% to 17%. Patients with severe stenosis of the vertebral artery, the basilar artery, or both are at particularly high risk of recurrent stroke despite antithrombotic therapy.
  2. II. Clinical presentation. Stroke type can vary and depends on the artery involved and if it is related to hypoperfusion and the extent of collateral, perforator involvement, or progression to complete occlusion. The majority presents with deep infarct or watershed infarcts.
  3. III. Diagnosis. In order of sensitivity and specificity, the gold standard conventional angiogram, computed tomography angiography (CTA), magnetic resonance angiogram (MRA), and transcranial Doppler ultrasound are used for diagnosis.
  4. IV. Treatment. A recent study showed no difference between aspirin (ASA) (325–1300 mg daily) and warfarin, although subsequent subgroup analysis showed minor benefit of warfarin over aspirin in basilar artery and intracranial vertebral artery stenosis. Intracranial balloon angioplasty and stenting can be an option in refractory cases that continue to have symptoms despite medical therapy but come with significant risk of stroke and mortality.
Aug 12, 2020 | Posted by in NEUROLOGY | Comments Off on I
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