UMEM Educational Pearls - Neurology

• Tramadol (Ultram) is an uncontrolled substance in the opiod family that binds mu receptors and is indicated for moderate to moderately severe pain.

• Tramadol lowers seizure threshold to < 1/100,000, likely related to its inhibition of neuronal re-uptake of serotonin and norepinephrine in the CNS.

• Concurrent use with SSRI's, TCA's, MAOI's, neuroleptics, other opiods, naloxone (when given for tramadol overdose) and alcohol exacerbates the risk of seizure onset.

• Tramadol-related seizure is independent of dose (i.e. can occur at starting dose of 25 mg), although brisk titration up to maintenance doses does increase seizure risk.
•  
•  To avoid triggering a seizure, tramadol should not be used in patients with the following conditions:

             --  seizure disorder

             --  alcohol withdrawal

             --  alcoholism

             --  drug withdrawal

             --  CNS infections

             --  metabolic disorder

             --  head trauma

• Don't forget to check for distal lower extremity neurologic deficit after knee injury, particularly when there is a direct blow to the popliteal fossa.
• The common peroneal and tibial nerves exit from the lateral and middle sections of the popliteal fossa, respectively.
• The common peroneal nerve wraps laterally around the fibula (where it's palpable), primarily supplying the lateral portions of the lower leg and foot.
• The tibial nerve primarily supplies the muscles of the posterior compartment of the lower leg (i.e. gastrocnemius, soleus, popliteus).
• Both the common peroneal and tibial nerve fibres branch into the sural nerve, which supplies the lateral foot.
• Common peroneal also splits into deep and superficial branches which supply the muscles of the anterior lower leg compartment and lateral lower leg compartment, respectively.  The deep branch also provides cutaneous innervation of the cleft between the great and second toes.

--  IN SUMMARY:

• Neurologic deficit of the posterior lower leg muscles likely = tibial nerve injury.
• Neurologic deficit of the anterior and lateral lower leg muscles likely =  peroneal nerve injury.
• Decreased sensation in the web space between the great and 2nd toes likely = (deep) peroneal nerve injury.
• Decreased sensation over the lateral dorsum of the foot likely = sural nerve injury.

*** Speaking of such deficits by naming the affected nerve distribution is particularly helpful when consulting orthopedists, neurologists, etc.

• The Sciatic Nerve is commonly injured during intramuscular buttocks injections as well as hip fracture dislocations and posterior dislocations.  In such instances, always confirm and document preserved sciatic nerve function.

• Sciatic nerve injury often results in foot drop due to decreased function of the hamstring, calf, and anterolateral lower leg muscles.

• Sciatic nerve injury may also cause loss cutaneous sensation over the calf , as well as the sole and lateral portions of the foot.

Top Reasons to call your Neurointerventionalist:

1. Vascular "blowouts" (i.e carotid tumor or trauma). 
2. Symptomatic dissections within 6 hours of onset (i.e. carotid or vertebral).
3. Ischemc Stroke with visible clot on CT angiogram outside of 3-hour IV tPA window.
4. Ischemic Stroke with visible clot on CT angiogram outside of 3-hour IV tPA window or with contraindication for tPA (i.e may be MERCI Device candidate).
5. Subarachnoid hemorrhage of aneurysmal origin.

• The Confusion Assessment Method (CAM) and Mini-Mental State Exam (MMSE)  can be used in combination to effectively differentiate delirium from dementia, respectively.
• CAM relies on observations by family members, caregivers, and clinicians to assess the following four symptoms:
  1. acute confusional onset
  2. inattention
  3. disorganized thinking
  4. ltered level of consciousness

 

• Using CAM, the diagnosis of delirium requires the presence of both the first and second features, plus one of the two other features.
• CAM is 95-100% sensitive and 95% specific for diagnosing delirium in the elderly.
• MMSE is not a diagnostic tool but identifies cognitive impairment suggestive of delirium by assessing orientation, short-term memory, calculation ability, and language (score 18-26 = mild dementia).
• A positive CAM and an MMSE score of > 25 is predictive of delirium.

 

• Poor differentiation of the type and cause of confusion in the elderly is associated with poor outcomes (i.e. increased mortality/morbidity, prolonged hospital stays, and functional decline).

• Confusion in the elderly can be categorized into three types with the following typical features:

1. Delirium - caused by organic illness, acute onset, agitated or drowsy, variable short-term memory, disorganized thoughts, hallucinations.
2. Dementia - chronic confusion due to long-term neurologic illness like Alzheimer's disease, progressive, irreversible, short-term memory loss, simple task performance and language impairment, aggression, personality changes.
3. Acute or Chronic Confusion - treatable illness (i.e. infection) triggers delirium in patient with baseline dementia.

• The ABCD and ABCD² scores are validated scales based on both prospective and retrospective data to assess patients' risk of stroke at 7 and 2 days after a TIA, respectively.  The biggest difference between the two is that the ABCD² Scale includes diabetes as a factor.

• ABCD Scale
• Age:  at least 60 = 1 point
• BP:  SBP > 140 and/or DBP > 90 = 1 point
• Clinical features:  unilateral weakness = 2 points; speech disturbance w/o weakness = 1 point;  any other neurologic  finding = 0 points.
• Duration:  at least 60 min. = 2 points; 10-59 min. = 1 point; < 10 min. = 0 points. 
• Score:  4 points = 1.1% risk;  5 points = 12.1% risk;  6 points = 31.4% risk.

• ABCD² Scale
• Age:  same as ABCD Scale
• BP:  same as ABCD Scale
• Clinical features:  same as ABCD Scale except "any other neurologic finding = 0 points" component is omitted.
• Duration:  same as ABCD Scale except  "< 10 min. = 0 points" component is omitted.
• Diabetes:  1 point
• Score:  4-5 points = 4% risk;  6-7 points = 8% risk;  0-3 points = 1% risk.

• Question = When considering sending a patient home prior to a thorough and appropriate TIA/stroke work-up, how low of a percent risk is acceptable?

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• One large study showed that cerebrovascular diseases represented the most common etiology of secondary epilepsy.
• Animal studies have shown most antiepileptic drugs to be neuroprotectants.
• Animal studies have also shown, however, that phenytoin, benzodiazepines, and phenobarbital may impair post-stroke motor recovery.
• Carbamazepine (Tegretol) has not been found to demonstrate any significant hinderance of  post-stroke recovery.
• From an anicdotal clinical perspective, levetiracetam (Keppra) is often used to treat post-stroke seizure.

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Treatment of Wernicke's Encephalopathy

Traditionally the treatment dose of thiamine in those that we suspect to have Wernicke's Encephalopathy is 100mg per day.  The problem is that this does was arbiarily picked by two physicians, Victor and Adams, in the 1950's.  They thought that 100mg a day would be a large dose. They also made their recommendation without fully understanding the pharmacokinetics of thiamine which has a half life of 96 minutes or less.  Compound this with case reports of individuals dying of Wernike's Encephalopathy despite being given 100mg of Thiamine daily.

Several authors are now advocating that patients with Wernicke's Encephalopathy be treated with 500mg of IV thiamine daily, but with the short half life some are advocating that the thiamine be given 2 to 3 times a day.  There are no good studies to refute or support the claims that higher doses are needed, but there are well documented cases of treatment failures at the lower dose.

PEARLs: 

• Consider high dose thiamine 500mg IV in patients that you are treating with Wernike's encephalopathy. 
• The 100mg dose is still appropriate for those that are just being suppliemented and in who Wernicke's encephalopathy is a consideation but not high up on the differential.

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• Seizures occur in 5-7% of patients within the first 24 hours of stroke.
• Although seizure prophylaxis is not indicated, prevention of subsequent seizures with standard antiepileptic treatment is recommended.

• Respiratory drive can be affected by injury to certain parts of the brain.  This is often seen in patients with traumatic brain injury (TBI).

• In the setting of TBI, recognizing abnormalities in respirations can be helpful in localizing the injury.

• Cheyne-Stokes respiration, in which breathing is rapid for a period and then absent for a period, is associated with injury to the cerebral hemispheres or diencephalon.

• Hyperventilation can occur when the brain stem or tegmentum is injured.

• Fractures of the orbital floor typically result from direct, blunt trauma with a rounded object to the eye. 

• When describing associated ophthalmic and/or neurologic injury, to consultants in particular, be aware of appropriate terminology to use in relaying the presence or absence of related physical findings.

• The following ophthalmic abnormalities are commonly associated with orbitla floor fractures:

              -- Enophthalmos (eye receded into the orbit) may occur when globe is 

                  displaced posteriorly, often with prolapse of tissue into maxillary sinus.

              -- Orbital dystopia (affected eye in a  lower horizontal plane than the other) may

                  occur due to the pulling of entrapped muscle and orbital fat.

• Remember to check for facial sensation, as decreased sensation along the ipsilateral cheek, upper lip, or upper gingiva suggests injury to the infraorbital nerve.

• The presence of a teardrop-shaped pupil suggests that the globe ruptured.

• 85% of TIA's last less than an hour.
• 25% of strokes are preceded by a TIA.

• Intracranial hemorrhage (ICH) can expand for the first 24 hours after onset.
• Peak ICH expansion occurs at 6 hours.
• REMEMBER:  The heads of patients with ICH should be elevated (~30 degrees) for at least 24 hours after the onset of bleeding to decrease the extent of expansion.  This is a simple, but too often neglected, clinical measure that potentially offers great benefit to the patient.

• A recent retrospecitve study of over 830 patients with suspected or confirmed benzodiazepine overdose from the Florida State Poison Center Database showed that only 0.7% experienced subsequent seizure or seizure-like acitivity (i.e. dystonia, muscle rigidity) after flumazenil administration.
• This study was conducted by emergency physicians from the University of Florida at Jacksonville where flumazenil is apparently often used as an antidote for benzodiazepine overdoses.
  

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• Myasthenia Graves (MG) is a chronic, autoimmune disorder which causes voluntary (skeletal) muscle weakness.
• In MG, antibodies block, destroy, or alter acetylcholine receptors at the neuromuscular junction (NMJ), which impedes nerve conduction to the muscle.
• The hallmark of MG is weakness, classically of the muscles controlling bulbar function, mastication, neck movement, and facial expression, that worsens with activity and improves with rest.
• A true MG crisis ensues once respiratory muscles weaken to the point of requiring assisted ventilation. Such a medical emergency can be triggered by fever, infection, or an adverse reaction to medication.
• Edrophonium chloride (or Tensilon) can be administered intravenously to confirm the diagnosis of an MG attack. This drug increases levels of acetylcholine at the NMJ and temporarily relieves the symptoms of an MG.
• Assisted ventilation, plasmpharesis, and high dose IV immune globulin can all be used to treat an acute MG crisis.
• MG can chronically be controlled with anticholinesterase agents such as neostigmine and pyridostigmine, as well as immunosuppressives such as prednisone, cyclosporine, and azathioprine. Thymectomy is also a surgical treatment option.

• Animal models have shown that neuroprotectants, including free radical trapping agents, decrease injury after ischemic stroke.

• NXY-059 is a promising neuroprotective agent that was studied in the SAINT I and II trials.

• SAINT I showed that NXY-059 used within 6 hours of ischemic stroke resulted in significant improvement in the primary outcome measure of reduced disability at 90 days.

• SAINT II was done to confirm the results of SAINT I with a larger study population, but unfortunately did not show any significant difference in mortality between NXY-059 and placebo.  There was also no difference in adverse reactions, however.

• More research is needed to determine the best neuroprotective agent to be used acutely for ischemic stroke.

• The future of emergency treatment of ischemic stroke will likely include such agents, to be administered by emergency physicians.

• The risk of symptomatic intracerebral hemorrhage after use of IV tPA for acute stroke is 6% (within 36 hours of administration).

The NINDS tPA Stroke Study Group.  "Intracerebral Hemorrhage after Administration of Intravenous tPA for Ischemic Stroke."  Stroke.  1997; 28:  2109-18.

• The Dix-Hallpike Maneuver is performed to help diagnose/rule out benign positional vertigo, a condition attributed to floating (canalithiasis) or fixed (cupulolithiasis) otoconial debris within the posterior semicircular canal of the ear.
• To perform, turn the patient's head 45 degrees to one side and then rapidly but carefully recline them backwards to a supine position, preferably with the head hanging partially off the bed (i.e. at a position about 10-20 degrees inferior to that of the rest of the body).  Next, perform the maneuver by turning the patient's head 45 degrees to the other side.
• If nystagmus is induced, the test is positive.  Note the following five characteristics of the nystagmus:  (1)  latency, (2)  direction, (3)  fatigue (i.e. extinguishes with repetitive maneuvers), (4)  habituation (i.e. duration), and (5)  reversal upon sitting upright.
• Note that the Dix-Hallpike Maneuver described here is the diagnostic version, not the one performed therapeutically, the latter of which is also helpful.