UMEM Educational Pearls - Neurology

• In patients presenting with bilateral miosis (i.e. pinpoint pupils) of unknown etiology, the astute clinician may consider acute pontine injury, opiate overdose, or medication-related causes as the source.
• In such cases, one should consider performing the simple corneal reflex test to evaluate mid and lower pontine function.
• This test consists of lightly touching the cornea with the cotton swab of a Q-tip and observing blink responses in both eyes.  It assesses afferent fifth nerve (sensory) and efferent seventh nerve (motor) function.
• A normal response is simultaneous (i.e. consensual) eye blinking.  An abnormal response may be manifest by midline deviation, followed by relaxation, of the lower eyelids.
• TAKE HOME POINT:  Corneal reflex testing is an easy way to help distinguish pontine injury from an opiate overdose in patients presenting with pinpoint pupils.  Confirmatory studies by way of brain imaging should follow.

• Marcus Gunn Pupil is a highly objective and significant clinical manifestation of a relative afferent pupillary defect (RAPD), indicating decreased pupillary response.

• The "swinging flashlight test" whereby a light is shone alternately back and forth between both eyes, can be used to elicit this finding.  A normal response results in constriction of both pupils, which indicates intact direct and consensual pupillary light reflex.  An abnormal response due to RAPD, however, results in minimal constriction of both pupils when the light in shone in the affected eye, causing one to perceive the presence of pupillary dilation.

• See the attached image which contrasts a normal response (top) to an abnormal response (bottom).

• Marcus Gunn Pupil is most commonly associated with lesions at the level of the optic nerve (proximal to the optic chiasm) or severe retinal disease.  Associated conditions include severe glaucoma, optic nerve tumors, and ocular trauma.

Attachments

• 1109281911_Marcus_Gunn_Pupil.jpg (35 Kb)

• The Glascow Coma Scale (GCS) was originally derived from data from adult head injuries; its use is therefore not always applicable or reliable in non-traumatic cases (particularly those which are complex) or children under a certain age.
• Scoring Range = 3 to 15.
• Severe is less than 9.
• Scores of 8 or less should prompt strong consideration for airway management via intubation.
• The motor score is the most predictive and clinically useful component.
• See GCS Score below:

EYE OPENING
4 = spontaneous
3 = to voice
2 = to pain
1 = none

VERBAL RESPONSE
5 = orientated
4 = confused
3 = inappropriate
2 = incomprehensible
1 = none

MOTOR RESPONSE
6 = obeys command
5 = localizes pain
4 = withdraw to pain
3 = decorticate
2 = decerebrate
1 = none

• Bell Palsy is a condition associated with the acute onset of facial paralysis due to palsy of the seventh lower motor neuron (cranial nerve seven).
• The presence of mastoid pain might be a diagnostic clue, as this symptom often precedes the onset of actual facial paresis.
• Other associated findings include:  typically unilateral facial muscle paralysis affecting both the upper and lower parts of the face; tear overflow and dry eyes; altered taste; hyperacusis or sound sensitivity; sensation spared; no other cranial nerves involved.
• It is often associated with viruses such as HIV, Epstein-Barr, and Hepatitis B, but most commonly herpes simplex.
• If facial paralysis is bilateral, consider Lyme disease as a possible etiology.

• Encephalitis, inflammation of the brain, is associated with the following signs and symptoms:  fever, headache, altered mental status, neurologic deficit, hallucinations, behavioral changes, photophobia, seizures, neck stiffness (when associated with meningitis), preceding viral prodrome, recent mosquito/tick/animal bites, and/or immunocompromised state/use of immunosuppressant medications.   
• The presence of focal neurologic deficit and/or altered mental status is more predictive of encephalitis than meningitis.
• The emergent management goal is to rule out and/or empirically treat bacterial meningitis and other treatable infectious sources such as Herpes Simplex Virus (HSV), Varicella Zoster Virus (VZV), and Cytomegalovirus (CMV); these carry significant mortality and morbidity risks.  Remember to have patient's cerebrospinal fluid (CSF) specifically analyzed for etiologies such as these (i.e. via PCR). 
• Treat presumed encephalitis aggressively by adding acyclovir to the antibiotic/steroid regimen administered, particularly when there is altered mental status and/or focal neurologic deficit.

• Delirium is a symptom, not a diagnosis; the astute clinician must seek to discover and treat the underlying source of delirious states.

• It is a transient cognitive condition associated with decreased attention span and waxing and waning symptoms.

• Three types: (1) Hyperactive, (2) Hypoactive, (3) Mixed (daytime somnolence, nighttime agitation).

• In young patients, the cause is commonly due to toxins or trauma, while that for the elderly is typically infection or medication related.

• Five critical causes of delirium that must be recognized and treated immediately:

1. Hypoxia
2. Hypoglycemia
3. Central nervous System infections
4. Hypertensive encephalopathy
5. Increased intracranial pressure

Show References

• While validated diagnostic tools such as the NIH Stroke Scale are often very helpful, particularly in terms of communicating with Neurologists, there are tools such as the ROSIER (Recognition of Stroke in the Emergency Room) Scale which is a brief score designed to facilitate expedited diagnostic testing and treatment of stroke in the emergency department.

• The ROSIER Scale has been found to recognize stroke with 93% sensitivity, 83% specificity, 90% positive predictive value, and 88% negative predictive value. 

• If the total score is > 0 (i.e. 1-6), then stroke is likely. If the total score is < or equal to 0, then stroke is unlikely, but can not be completely excluded.

• See attached ROSIER Scale for details.

Show References

Attachments

• 1108241811_ROSIER_Scale_for_Stroke.doc (61 Kb)

• The astute clinician should know the common causes of increased intracranial pressure (ICP) in order to recognize and treat this condition early.

• Below is a brief differential diagnoses for increased ICP due to structural abnormalities:

               -   Tumor - more likely if in lateral ventricles, posterior fossa, or intraspinal.

               -   Spina Bifida - blocked cerebrospinal fluid (CSF) flow may cause Chiari Malformation II.

               -   Congenital Aqueductal Stenosis - associated with mental retardation, abducted thumbs.

               -   Craniosynostosis - results from premature closure of skull sutures.

               -   Dandy-Walker Syndrome - cystic deformity of fourth ventricle, hypoplasia of cerebellar

                    vermis, and enlarged posterior fossa.

               -   Arachnoid Cyst - common locations include middle and posterior fossa.

Show References

• 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.

Show References

• 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."

Show References

• 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.

Show References

Attachments

• 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:

Show References

• 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.

Show References

• 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.

Show References

• 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.

Show References

• 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).

Attachments

• 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

Show References

• 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.