UMEM Educational Pearls - Neurology

• When performing a lumbar puncture, an opening intracranial pressure (ICP) greater than 20 to 25 mm of H2O is elevated.  

• If it is thought that a patient's headache is due to elevated pressure, cerebrospinal fluid (CSF) can be therapeutically removed.  It is typically recommended that the pressure not be lowered by more than 50% of the amount above which it is normal.

• The source of elevated ICP should be determined and addressed.  Common causes of increased intracranial pressure include:

             --- Venous drainage obstruction (i.e. cerebral venous sinus thrombosis).

             --- Endocrine (i.e. obesity, hypothyroidism, Cushing's disease, Addison's disease).

             --- Medications (i.e. vitamin A, cyclosporine, lithium, lupron, oral contraceptives,

                  amiodorone, and antiobiotics such as tetracyclines and sulfonamides).

             --- Other conditions (i.e. pregnancy, steroid withdrawal, acromegaly, polycystic ovary

                  syndrome, systemic lupus erythematosus, sleep apnea, HIV).

• While botulism is a rare condition (about 145 reported cases annually), it should still be considered in cases of descending neuromuscular weakness, as it can cause rapid loss of respiratory function and death (mortality < 8%).  Check patient's vital capacity.
• Botulism results from ingesting (onset of symptoms 6 to 48 hours) or having contamination of a wound (onset 4-14 days; associated with intravenous drug use) with Clostridium botulinum, an anaerobic, spore-forming bacteria; it has been used as a bio-terrorist agent as well.
• Patients typically present with anticholinergic symptoms and the four "D's" - (1) dry moth, (2) dysarthria, (3) diplopia, and (4) dysphagia.
• The definitive diagnosis is made by isolating the toxin in serum and/or stool.
• Treatment is supportive and might include use of equine trivalent anti-toxin and human botulism immunoglobulin.  Antibiotic and anti-cholinergic therapy has not been shown to be particularly effective.

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• Micturation syncope is a relatively rare phenomenon (2.4 to 8.4% of fainting episodes) which most commonly affects males, and can often be diagnosed by simply taking a thorough history.
• Straining to urinate triggers the vagus nerve which results in hypotension and bradycardia; in turn, cardiac output and brain perfusion is decreased, often resulting in diaphoresis, pallor, and weakness, followed by syncope or fainting. 
• This process is transient and vital signs as well as consciousness typically return to normal rapidly.
• When evaluating a patient for syncope, pay close attention for the presence of the following factors in order to make the diagnosis:

             -- occurs during or immediately following urination, often when bladder is full.

             -- occurs at night or after standing from the recumbent position of a deep sleep to urinate.

             -- risk factors: enlarged prostate, alpha blocker therapy, dehydration, alcohol, fatigue.

• Sometimes defecation, coughing, or severe vomiting can also result in syncope.

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• Seizures occur commonly and it is estimated that 1 of 26 people will develop epilepsy at some point in their life.
• A first seizure provoked by an acute brain insult is less likely to recur (3-10%) than a first-time unprovoked seizure (30-50% over the next 2 years).
• As an emergency provider managing an adult who presents with their first-ever seizure, there are four primary questions that require answering:

1. Was it in fact a true seizure? (often associated with tongue biting, urinary/bowel incontinence, preceding aura, post-ictal phase; examples of seizure mimics include syncope (i.e. cardiogenic, neurogenic, vasovagal), vertigo, myoclonic jerking, psychogenic convulsions, movement disorders.)
2. Does the patient have epilepsy? (defined a having at least 2 unprovoked epileptic seizures by any immediately identifiable cause.)
3. What type of epilepsy? (cryptogenic (i.e. of unknown etiology) or symptomatic (i.e. caused by prior central nervous system insult such as brain injury.)
4. What is the cause? (metabolic panels to assess for uremia, electrolyte and glucose abnormalities, and drug intoxications should be performed, as well brain imaging to determine the presence of focal intracranial lesions.)

• Many patients do not require anticonvulsant medication following a single, first time seizure; A general consensus is that such therapy should be strongly considered for initiation after a second episode of seizure activity. 

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• Studies have shown that the natural history of Bell's Palsy without treatment is such that 85% show signs of recovery within 3 weeks of symptom onset, and 71% experience complete recovery.
• Of the remaining individuals who do not completely recover, 13% experience persistent mild sequelae and 16% have residual weakness, synkinesis, and/or contracture.
• Those with incomplete lesions (i.e. incomplete paralysis) are more likely to return to normal function (94%), while only 60% of those with clinically complete lesions return to normal function.
• Herpes zoster is associated with more severe paresis and a worse prognosis.  When little to no recovery is seen within the first 21 days following symptom onset, the prognosis is less favorable.

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• Myasthenia Graves (MG) is an autoimmune disorder wherein antibodies attack acetylcholine nicotinic postsynaptic receptors at the myoneural junction, resulting in muscle fatigue (commonly bulbar) that worsens with use and improves with rest.  MG flares are most commonly due to infection or inadequate treatment with cholinesterase inhibitors.

• The Tensilon (edrophonium) challenge test can be used to help distinguish an MG crisis from a cholingergic crisis.  Once the airway and ventilation are secure, escalating doses of edrophonium (i.e. 1 mg, then 3 mg, then 5 mg, up to a maximum of 10 mg total) can be administered with the goal of relieving the muscle weakness.  If a true MG crisis is present, patients usually respond with dramatic improvement within 1 minute.  Patients having a cholinergic crisis, on the other hand, typically respond with increased salivation, bronchopulmonary secretions, diaphoresis, and gastric motility.  

• Monitor closely as edrophonium can cause significant bradycardia, heart block, and asystole (only 0.16% risk by reports, but have atropine nearby). 

• Once the edrophonium wears off, patients having an MG crisis may develop increased secretions and respiratory distress as their muscle weakness returns, so manage expectantly and with caution.  

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• Remember that lithium overdoses should not be treated with oral activated charcoal, as these charged particles are not adequately absorbed by this method.
• Instead, whole bowel irrigation using 500 mL to 2 liters of polyethylene glycol should be administered within the first 2-3 hours of presumed large ingestions (ie. at least 10 to 15 pills), with a goal of having the patient pass stool to the point of clear rectal effluent.
• Hemodialysis (HD) should be reserved to treat severe lithium toxicity, which is somewhat loosely defined as a serum level greater than 3.5 to 4 meq/L (mmol/L). 
• For levels > 4 meq/L, most experts agree that HD should be performed regardless of whether associated symptoms are present.  For levels > 2.5 meq/L with associated clinical signs/symptoms (i.e. tremulousness, dizziness, lethargy, seizure), conditions that would limit lithium excretion (i.e. renal insufficiency), or conditions that would limit ability to aggressively hydrate (i.e. CHF), HD should be performed.   

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• A huge limitation to effectively managing acute ischemic stroke in rural areas is the frequent lack of access to local experts in vascular neurology.  While most guidelines encourage the use of telemedicine to overcome such barriers, the start up costs of such programs are sometimes prohibitive, particularly for small, rural practices. 
• A recent, small study showed that providers may be able to use the iPhone as a primary or adjunctive tool with telemedicine, to properly diagnose and manage acute stroke.
• The study compared a face-to-face provider's NIH Stroke Scale (NIHSS) interpretation to that of a remote provider using an iPhone with FaceTime software that allows real-time streaming of audio and video.
• Agreement between providers was excellent (intraclass correlation coefficient 0.98); the NIHSS score of the providers did not differ by more than 1 point in 17 of the 20 cases; in only one category - ataxia - was agreement poor.
• TAKE HOME POINT:  Streaming real-time video technology may offer an effective and economically feasible alternative to suboptimal acute stroke care in rural areas or an alternative/adjunct to pure telemedicine programs.  (This is not an advertisement or endorsement for the iPhone.)

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• Myasthenia Graves (MG) is often associated with several, distinct clinical findings which patients may have during their crisis in the emergency department. These findings may include the following:

              -  Mask-like face

              -  Eyelid weakness 

                    --  leads to ptosis

                    --  exacerbated by sustained upward gaze

                    --  improved by closing the eyes for a short while

                -   Extraocular motion abnormality

                     --  usually affects more than one extraocular muscle

                     --  may be assymetrical

                     --  may result in mild proptosis

                 -   Weak palatal muscles

                      --  nasal-sounding voice

                      --  nasal regurgitation of food

                  -  Weak jaw muscles

                  -  Absent gag reflex

                  -  Pupils normal

Differentiating Central Retinal Artery vs. Vein Occlusion Fundoscopically

• While there are several historical and clinical features that differentiate central retinal artery (CRA) occlusion from central retinal vein (CRV) occlusion, the fundoscopic examination can also be used to distinguish between the two.
• In CRA occlusion, the retina appears grossly swollen and pale, with a prominent fovea that would otherwise be obscured by a normal, pinkish-red background (see attached - Image 1).
• In CRV occlusion, the disc is massively swollen with splotches of hemorrhage and cotton wool spots diffusely (see attached - Image 2).

Attachments

• 1110191840_Fundoscopic_Images_of_Central_Retinal_Artery_and_Vein_Occlusion.pdf (103 Kb)

• The Straight Leg Raise (SLR) test can be used to determine if patient has true sciatica.
• The patient lies supine with one leg either straight or flexed at the knee with the sole of the foot flat on the stretcher.
• The other (affected) leg is kept straight and raised up by the examiner.
• The test is positive when raising the leg between 30 to 70 degrees causes pain to occur and radiate down the leg to at least below the knee, and often all the way down to the great toe (sensitivity 91%, specificity 26%).
• Sensitivity may improve with dorsi-flexion of the foot while the leg is elevated.
• The following do NOT indicate a positive test:  pain of lower back only, without radiation to below knee; overtly excessive pain behavior; patient contraction of antagonist muscles that limit examiner's testing; tightness of buttock and hamstring muscles; nonspecific complaints.
• The SLR test can also be performed with the patient in a sitting position, by stretching the sciatic nerve by extending the knee; the test is positive if pain radiates to below the knee.

• A normal corneal reflex is usually ABSENT in the setting of pontine injury, and typically PRESENT in patients presenting with an opiate overdose.

• 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

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• 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.

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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.

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