UMEM Educational Pearls - Neurology

• Infectious disease guidelines recommend that antibiotics be administered to patients in whom bacterial meningitis is suspected within 30 minutes of their presentation.
• Antibiotics do not appear to cause changes in cerebrospinal fluid (CSF) white blood cell, protein, or glucose levels which are compatible with impeding diagnostic utility.
• Additionally, CSF gram stain findings are not significantly changed by early antibiotic use, as these studies have been found to be diagnostic in most patients even if lumbar puncture (LP) is delayed by up to 3 days. 
• CSF cultures may be positive even after a single dose of antibiotics, although the yield decreases with more fastidious organisms such as meningococcus.
• In 86% of patients with bacterial meningitis, the causative organism may be isolated pre-antibiotic administration via blood culture.
• TAKE HOME POINT:  In cases of high suspicion for bacterial meningitis, do not delay administering antibiotics for the sake of first performing an LP, and have a low threshold to check blood cultures.

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• There is a host of contraindications to using thrombolytic therapy to treat acute ischemic stroke (AIS), one of which is recent surgery.

• It is likely that the quantity of patients presenting with AIS following oral surgery will rise given the increasing use of implants and more frequent discontinuation of anti-coagulants prior to dental procedures.

• While there is not much data on the risk of bleeding after use of thrombolytics in patients who have recently undergone minor dental surgery, some case reports have shown there to be an association with substantial hemorrhage.

• TAKE HOME POINT:  Remember to consider minor surgical procedures, such as dental, as a contraindication when screening acute stroke patients who are potential candidates for thrombolytic therapy; often, patients and their family members may not consider such procedures to be "surgery."

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• Central Pontine Myelinolysis (CPM) is a largely irreversible, dreaded neurologic complication caused by osmotic demyelination, as a result of increasing sodium levels too rapidly.  It is definitively diagnosed via Brain MRI.

• Symptoms may include dysphagia, dysarthria, paraparesis, quadriparesis, lethargy, seizure, or even coma, and usually begin within 2 to 6 days following sodium elevation (i.e. may not be apparent in the emergency department).

• If the hyponatremic patient is symptom-free, treat conservatively by restricting oral fluid intake to less than 1500 mL per day.  Isotonic fluids (i.e. 0.9% normal saline) may be used, particularly if the patient is dehydrated.

• If the hyponatremic patient is symptomatic, hypertonic saline (i.e. 3%, start with 100 mL bolus) may be used.

• Increase sodium level by no more than 1.5 to 2 meq/L per hour for the first 3 to 4 hours until symptoms resolve.  Increase by no more than 10 meq/L in the first 24 hours.

• Take Home Point:  Prevent devastation of CPM by treating asymptomatic hyponatremia conservatively and by closely monitoring rate of sodium increase.

• Posterior Reversible Encephalopathy Syndrome (PRES) is a relatively newly-recognized condition characterized by headache, convulsions, confusion, and vision loss (i.e."CCCV," "Cephalgia,Convulsions, Confusion, Vision loss.")

• Risk factors include:  severe hypertension, eclampsia, renal failure, and use of immunosuppressive medications such as tacrolimus and cyclosporine; low magnesium levels may exacerbate PRES.

• PRES may be under-recognized because its diagnosis is based on both clinical and radiographic findings.  Brain MRI findings classically show bilateral hyperintense densities in the parieto-occipital regions on T2 weighted images (see attached image).

• Treatment of PRES consists of managing the underlying cause such as lowering blood pressure and discontinuing offending medications, which typically results in resolution of symptoms.

• Take Home Point: Consider PRES as the etiology of unexplained constellations of symptoms including headache, seizure, confusion, and vision loss in the setting of severe hypertension, particularly amongst patients with renal failure and on immunosuppressants.

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• 1107201545_PRES_MRI.jpg (13 Kb)

• Emergency Department (ED) management of Multiple Sclerosis (MS) includes two components:

              (1) immunomodulatory therapy for the underlying immune disorder, often with high dose 

                    intravenous (IV) steroids which speeds recovery, and

              (2) management of symptoms through supportive measures and amelioration of risk factors

                    associated with precipitating acute exacerbations such as infection through aggressive use

                    of antibiotics.  Treatment of fever with antipyretics also key as even small increases in

                     temperature can significantly affect conduction through partially demyelinated fibers.

• In patients with fulminant MS or disseminating acute encephalitis, management includes the following:

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• Transient Ischemic Attacks (TIA's) are warning signs of something worse to come and must not be ignored.
• Within 90 days of a TIA, about 10.5% of patients go on to have a full blown stroke, half of which occur within 1 to 2 days of their emergency department visit.
• Have an extremely low threshold to admit TIA patients in order that a work-up to determine the source and risk factors can be completed promptly.
• The typical TIA work-up consists of a brain CT, brain MRI, an electrocardiograph and cardiac monitoring (to evaluate for arrhythmia such as atrial fibrillation), echocardiogram (to evaluate heart function, check for a patent foramen ovale and clots), and carotid doppler ultrasound (to evaluate for atherosclerotic disease).

• Don't forget to give aspirin to patients presenting with acute ischemic stroke (AIS).

• Large trials such as the International Stroke Trial (IST)  and Chinese Acute Stroke Trial (CAST) have shown that starting 160 to 300 mg of aspirin within 48 hours of the presumed onset of ischemic stroke reduces the risk of early recurrent ischemic stroke, with no major increased risk of hemorrhagic conversion and with improved long-term outcome.

• Studies have also shown that high and low doses of aspirin (30 to 1200 mg per day) after AIS yield similar efficacy for preventing vascular events, but that higher doses are associated with a greater risk of gastrointestinal hemorrhage.

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• Idiopathic Intracranial Hypertension (IIH), previously known as Pseudotumor Cerebri, should be considered as a possible etiology of recurrent, often daily, headaches, particularly in obese, female patients.

• The pain is typically throbbing, sometimes unilateral, and severe.  In addition to headache, these patients often present with transient visual abnormality (72%), pulsatile tinnitus (60%), photopsia (seeing lights, flashes, colors) (54%), retrobulbar pain (44%), diplopia (38%), and sustained visual abnormality (26%).

• The most commonly encountered physical examination findings are (1) papilledema - the greater, the higher the risk for vision loss, (2) visual field loss (always check!), and (3) sixth cranial nerve palsy - due to increased pressure on this long-coursing intracranial nerve.

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• A persistent systolic blood pressure (BP) > 185 and/or a diastolic BP > 110, is a contraindication to thrombolytic therapy in acute ischemic stroke patients.

• In cases such as these, the following antihypertensive regimens may be used in order to attempt to proceed with administering thrombolytic therapy as soon as possible:

1. Nicardipine infusion 5 mg/hour; titrate up by 2.5 mg/h every 5 - 15 minutes as needed to a maximum of 15 mg/h; reduce to 3 mg/h once desired BP is reached,
2. Labetalol 10-20 mg IV over 1-2 minutes; may repeat once, OR
3. Other agents such as hydralazine or enalapril when appropriate.

• Note that these options are based on 2010 recommendations which no longer include the use of nitropaste, as was the case with the prior recommendations from 2007.

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• Visual fixation typically suppresses nystagmus caused by a peripheral lesion, but it does not usually suppress nystagmus from a central lesion. It may be therefore be helpful to manipulate a patient's visual fixation to determine whether their nystagmus is due to a central or peripheral lesion.
• Frenzel lenses (see attached picture) are large magnifiers that blur vision and inhibit visual fixation.  When a patient looks through this type of lens, one would expect peripheral nystagmus to increase, as visual fixation would be inhibited.
• If Frenzel lenses are not available, ask the patient to maintain their visual gaze on a single location to reproduce visual fixation.  Then note whether the nystagmus ceases (i.e. peripheral lesion) or continues (i.e. central lesion).

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• 1106081213_fresnel-lens.jpg (14 Kb)

• Distinction between central and peripheral vertigo can be made clinically by way of close physical examination of nystagmus.  The chart below describes specific findings for each:

• 	PERIPHERAL	CENTRAL
  Nystagmus
  Direction	Fast phase away from lesion; never reverses direction	Sometimes reverses direction if looking in direction of slow phase
  Type	Horizontal with torsional component, never purely torsional or vertical	Can be in any direction
  Other neurologic signs	Absent	Often present
  Postural instability	Unidirectional instability, walking preserved
  Effect of visual fixation	Suppressed	Not Suppressed
  Deafness or tinnitus	May be present	Absent

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• Ischemic cerebellar strokes are often associated with posterior inferior cerebellar artery (PICA) insufficiencies.   
• Unlike vertebrobasilar strokes which typically present with vertigo accompanied by evidence of of brainstem ischemia like diplopia, dysarthria, dysphagia, and numbness, cerebellar strokes may present with isolated vertigo, making the diagnosis elusive given the challenging task of differentiating a central from peripheral process.  
• Central vertigo, particularly when due to cerebellar infarct, tends to be associated with severe gait instability, such that the patient often falls while walking, nystagmus which may be multi-directional or purely vertical, and deafness or tinnitus tend to be absent.
• Given that edema formation and mass effect are more likely to result from cerebellar infarcts as compared to other types of strokes, these patients are often best served in an intensive care setting for at least the first 24 hours following onset. 

• Treating stroke patients older than age 80 with intravenous tissue plasminogen activator (IV-tPA) continues to be a controversial topic, primarily due to its perceived association with increased rates of intracranial hemorrhage (ICH).

• Reliable analysis of robust datasets from the Safe Implementation of Treatment in Stroke-International Stroke Thrombolysis Register (SITS-ISTR) has shown that, in fact, IV-tPA patients older than age 80:

             (1) do not have increased risk for clinically significant ICH,

             (2) have early clinical improvement similar to younger patients, and

             (3) have poor outcomes related to increased mortality (odds ratio 30% versus 12%), rather than

                   to higher rates of functional dependence (i.e. Modified Rankin Score 3 to 5). 

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Causes of Pulsatile Tinniitus 

• Pulsatile tinnitus, also known as objective tinnitus, results from altered blood flow or increased blood turbulence near the ear.  People other than the person experiencing the tinnitus are often able to hear this rhythmic, pulse-patterned noise.  
• While there are several benign causes of pulsatile tiniitus such as strenuous exercise, atherosclerosis, and ruptured tympanic membranes, there are only a few serious etiologies.
• It is important that the astute emergency provider be aware of and know the appropriate treatment for the following life-threatening and/or high morbidity-associated causes of pulsatile tinnitus:

1. Idiopathic intracranial hypertension (previously known as pseudotumor cerebri)
2. Carotid artery aneurysm
3. Carotid artery dissection
4. Vasculitis such as giant cell arteritis  

Lithium Toxicity

• Lithium toxicity is common and occurs in 75 to 90% of patients receiving long-term lithium therapy at some point during their management.  It most often results from inadequate renal excretion.
• Toxic patients typically present with mild side effects such as hand tremor, but other symptoms like weakness, delirium, rigidity, hyperreflexia, altered gait, seizure, and EEG changes may also result.
• While severe lithium toxicity typically correlates with elevated serum levels, not all patients with high lithium levels present with advanced symptoms, at least in the early stages; this is due to delayed distribution within tissues.  Similarly, patients with lower serum levels of lithium may present with advanced symptoms, if the drug has accumulated in the cerebrospinal fluid to a greater extent than it has the serum. 

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Contraindications to performing lumbar puncture (LP):

- INR > 1.4 or other coagulopathy

- Platelets < 50

- Infection at desired puncture site

- Obstructive / non-communicating hydrocephalus

- Intracranial mass

- High intracranial pressure (ICP) / papilledema (relative contraindication depending on etiology; especially a concern with intracranial mass lesion secondary to the increased risk of transtentorial or cerebellar herniation)

- Focal neurological symptoms/signs, decreased level of consciousness

- Partial / complete spinal block

- Acute spinal trauma

• Patient positioning is key when measuring opening pressure (OP) of cerebrospinal fluid (CSF) during lumbar puncture. 

• OP is only accurate when measured while the patient is completely horizontal and relaxed, in the lateral decubitus position (i.e. no neck flexion or extension, legs extended, no valsalva).  In order to achieve this, you may need to carefully place patient in a lateral decubitus position if they are initially sitting upright prior to dural puncture and/or be sure to have patient straighten their legs (i.e. abort fetal position) once ready to measure OP.

• Strictly speaking, normal range of CSF pressure is 8 to 21 cm, but obesity can increase it up to 25 cm and still be considered normal.  Thus, while the significance of measurements between 20 and 25 cm in obese patients may be unclear, levels above 25 cm are always abnormal.

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• Chemoprophylaxis should be given to those individuals who came into "close contact" with someone infected with meningitis due to meningococcal infection (i.e. Neisseria meningitidis).  It should be given as early as possible following the exposure; when there is a high index of suspicion, do not wait for culture results to give prophylaxis.
• Chemoprophylaxis is generally not indicated when the etiology is Streptococcus pneumoniae, and should be reserved for young children who have not received a Haemophilus influenzae type b (Hib) vaccination and immunocompromised close contacts when the etiology is Hib.
• While the definition of a "close contact" remains somewhat ambiguous, it generally refers to individuals who have had prolonged (>8 hours) contact while in close proximity (<3 ft) to the patient, or who have been directly exposed to the patient's oral secretions between one week prior to the onset of the patient's symptoms until 24 hours after initiation of appropriate antibiotic therapy.
• Standard regimens for antimicrobial prophylaxis include ciprofloxicin, ceftriaxone, and rifampin.  Adults typically require a single oral dose of 500 mg of ciprofloxicin or 250 mg of intramuscular (IM) ceftriaxone, while individuals under age 15 may receive a single dose of 150 mg of IM ceftriaxone.

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• Trigeminal Neuralgia (TN) presents with unilateral, lancinating head and facial pain, affecting one or more of Cranial Nerve V's divisions.

• The pain occurs in 1 to 5 second multiple attacks throughout the day.  Symptoms may remit and recur.

• TN is associated with trigger points, but lacks any associated focal neurologic deficit or abnormality.

• These characteristics will help distinguish TN from other sources of unilateral headache, such as migraines, cluster headaches, sinusitis, and glaucoma.

• There are a host of treatments for TN, including options such as medical management with anti-convulsants and/or muscle relaxants, surgical ablation, alcohol injection (induces numbness), glycerol injection (destroys affected part of nerve), balloon compression, and administration of electrical current.

• Medical management with analgesics and muscle relaxants is typically the most appropriate, first-line treatment in the emergency department.

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• Myasthenic patients who initially present in a stable fashion with normal ventilation and minimal dyspnea can decompensate rapidly.
• In Myasthenia Gravis, the body produces antibodies against native post-synaptic acetylcholine (Ach) receptors. Adding a paralytic that occupies the few remaining functional Ach receptors could significantly prolong general muscular dysfunction and the need for ventilatory support during a myasthenic crisis.
• If intubation is required, DO NOT administer neuromuscular blocking/paralytic agents such as succinylcholine or rocuronium, as these agents antagonize Ach binding receptors at the post-synaptic membrane of the neuromuscular junction.
• Studies have shown that the use of propofol and fentanyl, without any paralytic, provides sufficient analgesia and sedation to successfully complete a humane intubation in these cases.
  
   

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