UMEM Educational Pearls - Neurology

Below is an edited version of this week's neurological clinical pearl. Somehow the scores and their definitions showed up incorrectly matched.  See corrections below.

• Verbal function is one of the three neurologic responses assessed by the Glasgow Coma Scale ( GCS).
• This response is scored on a scale of 1 to 5, 5 being the best response.
  • 5 = Oriented (responds coherently and appropriately to questions such as name, age, situation).
  • 4 = Confused (responds to questions coherently but with some disorientation and confusion).
  • 3 = Inappropriate words (random articulated speech but no conversational exchange).
  • 2 = Incomprehensible sounds (moaning but no words).
  • 1 = No verbal response.

• Eye function is one of the three neurologic responses assessed by the Glasgow Coma Sacle ( GCS).
• This response is scored on a scale of 1 to 4, 4 being the best response.
  • 4 =  Spontaneous eye opening.
  • 3 = Eye opening in response to speech (not to be confused with eye opening in an asleep patient when prompted with speech; these would receive a 4, not a 3).
  • 2 = Eye opening with painful stimuli (i.e. nailbed pressure, supraorbital compression, and/or sternal rub).
  • 1 = No eye opening.

• Glasgow Coma Scale (GCS) is a validated score intended to provide a reliable and objective method for recording and communicating a patient's consciousness.
  

• It was originally created to assess head injury patients' neurologic status/deficit.
  

• The scale ranges from 3 (deeply unconscious) to 15 (fully awake).
  

• It tests the following three responses:  (1) eye, (2) verbal, and (3) motor, listed in order of increasing functional significance with regard to status (i.e. optimal eye response assigned lower score (best score = 4), followed by a best score of 5 for verbal response, and optimal motor function being scored at 6.

• The most common anatomical locations for ischemic stroke are in the internal capsule and the basal ganglia.
• Look for hypodensity (i.e. darkening which suggests edema) in these parts of the brain on CT when trying to locate areas of stroke.
• Acute stroke typically takes at least 3 hours to manifest in the form of edema on Head CT.  The larger the stroke, the quicker the abnormality is seen.

• Despite guidelines that recommend against opioid use as first-line treatment for migraine headaches,  meperidine (Demerol) is still administered in 36% of all migraine headache ED visits in the U.S.

• Meperidine's lack of efficacy, adverse effects such of seizure, and toxic metabolic accumulation all contribute to its use for migraine headaches being discouraged.

• A recent meta-analysis out of New York again supports the avoidance of using meperidine for migraine headaches, and instead, encourages clinicians to use anti-emetic and dihydroergotamine regimens.

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Important things to document in acute ischemic stroke cases from a medicolegal aspect:

-- time of onset
-- time of diagnosis
-- why tPA given or not given (the longer note for NOT giving it; 90% of related litigation cases based on NOT giving tPA.)
-- date and time on each side of note of every page
-- make it legible
 

** Fosphenytoin (Cerebyx) is a pro-drug of Phenytoin (Dilantin).

** Differences between fosphenytoin and phenytoin are primarily due to fosphenytoin being more water soluble.
 

Fosphenytoin versus Phenytoin:
•     Fosphenytoin  >  less risk for cardiac-related adverse effects (propylene glycol not required for solubilization)
•     Fosphenytoin >  lower risk of local skin and subcutaneous irritation during infusion 
•     Fosphenytoin > can be given intramuscularly
•     Fosphenytoin >  can be infused at a faster rate (20 mg/kg phenytoin equivalents (PE’s) load at a rate of 100 to 150   mg of PE’s/minute) due to its safer side/adverse effects profile.

• Phenytoin (Dilantin) should not be infused at a rate greater than 50 mg/minute, to a total of 20 mg/kg.

• Caution is encouraged while infusing due to the risk of inducing hypotension and cardiac arrhythmias, making cardiac monitoring during infusion mandatory.

• These adverse effects are partly related to the propylene glycol used to solubilize phenytoin.

• Additionally, the risk of local pain and injury, such as venous thrombosis and the purple glove syndrome, increases with rapid infusion rates.

• Exact definitions of status epilepticus vary. 

• Generally speaking, status epilepticus is defined as a single unremitting seizure that lasts longer than 5 to 10 minutes OR greater than one generalized clinical seizure with no interictal return to clinical baseline.

• While treatment with phenytoin and diazepam is often used for status, studies have shown that lorazepam use alone is more effective. 

• Chiari Malformations are congenital abnormalities wherein the cerebellum downwardly displaces into the spinal canal.
• This results in an increase in pressure and subsequent obstruction of CSF flow.
• Common symptoms associated with Chiari Malformations include:

              -  vertigo

              -  headache

              -  muscle weakness

              -  coordination abnormalities

              -  gait abnormalities

              -  visual abnormalities

• It is crucial to be familiar with and use  the NIH Stroke Scale (NIHSS) to objectively describe the extent of a stroke, in a language universal to all physicians, particularly our neurology colleagues.
• This validated tool consists of 15 items and the scale ranges from 0-42.  The higher the number, the worst the stroke.
• The NIHSS does not have to be memorized, but rather accessible for reference when needed.
• Studies have validated an abbreviated, 5-item NIHSS that has the same predictive performance as the 15-item scale.  This scale ranges from 0-16.
• While this abbreviated scale was created primarily for use in the prehospital setting, it can certainly be performed in the ED prior to rushing the patient off the CT for a head scan, in order to provide your neurologist with some objective information in a timely fashion.
• The NIHSS-5 assesses the following functions, in decreasing order of importance in terms of prognosis:

              --  motor function (right leg)

              --  motor function (left leg)

              --  gaze

              --  visual fields

              --  language

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• There is mounting evidence in favor of effectively treating migraine headaches with antiemetic dopamine antagonists such as metoclopramide (Reglan) and prochlorperazine (Compazine) as primary parenteral management.

• Diphenhydramine (Benadryl) can be administered simultaneously with such agents to prevent akathisia and dystonic reactions.

• Apart from the prophylactic effects of diphenhydramine, it may also play a synergistic role is actually treating the symptoms.

• A recent study (Friedman, et al) showed no significant difference in the efficacy or adverse events of treating migraine with 20 mg of metoclopramide plus 25 mg of diphenhydramine versus 10 mg of prochlorperazine plus 25 mg of diphenhydramine, although there was an insignificant trend in favor of prochlorperazine lowering the pain score to a greater degree.

• Note that the 20 mg dose of metoclopramide is higher than what is traditionally used in most emergency departments, but escalating the dose of up to 20 mg over a few hours may be more efficacious (the slower the administration and the simultaneous use of diphenhydramine decreases risk of dystonic reactions).

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-- Tourette Syndrome (TS) is an inherited neurological disorder characterized by repetitive involuntary movements and uncontrollable vocal sounds called tics.
-- Underlying defect is unknown; however, research suggests that it could be caused by abnormalities in serotonin and dopamine activity within the basal ganglia.
-- Associated behavioral problems include OCD, ADHD, anxiety, and depression.
 

Diagnostic criteria:

• Encephalomalacia, also known as cerebromalacia, is a softening of brain tissue that results from ischemia or inflammation, most typically due to vascular insufficiency or degenerative changes.

• On Brain CT, it appears as a darkened area and can be confused for cerebral edema due to acute ischemia (i.e stroke).

• Unlike edema, encephalomalacia on CT is often accompanied by:

                    ---  well defined, circular vacuoles

                    ---  presence of good gray-white matter differentiation in surrounding areas

                    ---  a lack of significant effacement or lost of sulcus definition

                    ---  a history of prior stroke or head injury

• Acceleration, deceleration, and rotational forces cause diffuse axonal injury (DAI).
• It is characterized by widespread shearing and retraction of axons during traumatic brain injury (TBI).
• DAI often results in coma and is associated with poor prognosis.
• In addition to cortical white matter injury, it often also involves the corpus callosum, basal ganglia, brainstem, and cerebellum.
   

tPA should NOT be used to treat ischemic stroke in the following instances:

• Platelet count < 100,000
• INR > 1.7 or PT > 15
• Heparin administration within past 48 hours with subsequent PTT above upper limits of normal

• Arteriovenous malformation (AVM) is a congenital defect of the circulatory system, comprised of a nest of blood vessels.
• AVM is typically detected incidentally during CT or MRI studies.
  
• Symptoms vary depending on the location of the AVM and the amount of hemorrhage, but can be as general as a seizure or headache.
• The following clinical symptoms commonly occur with AVM bleeds:
  

• Asterixis is a tremor of the wrist that occurs when the wrist is extended (dorsiflexed).
• It is also often referred to as a "flapping tremor" or "liver flap."
• Asterixis results from arrhythmic, interrruptions of voluntary muscle contraction resulting in brief lapses in posture.
• It is most often associated with hepatic encephalopathy that results from abnormal metabolism of ammonia to urea, causing brain cell damage.  The subsequent elevated levels of ammonia are due to liver failure.
• In addition to hepatic enephalopathy, asterixis can also be associated with the following conditions:

               -- azotemia

               -- cardon dioxide toxicity

              -- metabolic encephalopathies

              -- Wilson's Disease

• Anisocoria is when pupillary size is assymetric.

• Anisocoria suggests a lesion in the efferent fibers supplying the pupillary sphinter muscles.

• In order to localize the causative lesion, you must first determine which pupil is abnormal, the smaller one or the larger one.

• The smaller pupil is abnormal when the degree of assymetry is more pronounced in darkened settings.

• The larger pupil is abnormal when the degree of assymetry is more pronounced in bright light.

• Most studies suggest that the risk of aneurysm rupture significantly increases after the size of 7 mm.

• The risk of rupture is greater for posterior circulation aneurysms.

• Five-year risk of aneurysmal rupture based on size (for anterior and posterior circulation aneurysms, respectively):
  
  ---  7 to 12 mm --> 2.6 and 14.5%              

             ---- 13 to 24 mm --> 14.5 and 18.4%