UMEM Educational Pearls - Neurology

• While seizure patients are often treated with common antiepileptics such as phenytoin and levetiracetam, those with severe refractory disorders may be treated with less frequently used medications such as felbamate.
• Felbamate is reserved as monotherapy or adjunctive therapy for refractory, partial seizures in adults with or without secondary generalized seizure, and as adjunctive therapy for children with partial and generalized seizures due to Lennox-Gastaut Syndrome (condition that causes seizures and developmental delay).
• In patients who present to the ED on felbamate, consider checking a CBC with differential and liver function tests, as it can cause aplastic anemia (relatively rare but 30% fatal) and liver damage (rare but 40% fatal), respectively.
• Signs and symptoms of aplastic anemia include:  fever, sore throat, chills, other signs of infection, bleeding, easy bruising, extreme fatigue, weakness, or lack of energy.
• Signs and symptoms of liver failure include: nausea, extreme fatigue, unusual bleeding or bruising, lack of energy, anorexia, right upper quadrant pain, jaundice, or flu-like symptoms.

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• Ischemic strokes often present as lacunar infarcts, wherein flow along the deep penetrating vessels of the middle cerebral artery is compromised.
• These strokes typically present with either purely motor or purely sensory neurologic deficit, in an ipsilateral pattern, often striking parts of the basal ganglia.
• Lacunar infarcts may present in a mild manner and carry the best prognosis for recovery relative to other types of ischemic stroke.

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• Lhermitte's phenomenon is a transient, sensory symptom which likens an electric shock that radiates down the spine or into the limbs.

• The sensation is triggered by neck flexion.  The frequency with which they occur varies and the slightest movement of the head or neck may trigger it.

• This phenomenon occurs most frequently with multiple sclerosis, but can also be seen with other lesions of the cervical cord, including tumors, disc herniation, post-radiation myelopathy, and following trauma.

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• Transverse Myelitis (TM) is the development of grey and white matter inflammation of the spinal cord, which can result in demyelination.
• Hallmark characteristics of this condition include: (1) isolated spinal cord (not brain) dysfunction, and (2) the lack of associated cord compression.
• TM can be acute or subacute, such that it progresses over the course of hours to several days.  Nearly half of cases will reach its maximal deficit within 1 to 10 days of onset.
• The diagnosis of TM is primarily based on the history and physical examination findings.  MRI of the spinal cord and myelography are often used as diagnostic adjuncts.
• This condition typically presents with paresthesias, back pain, and ascending leg weakness.
• Febrile illnesses often serve as a precursor; one series found this to be the case in 37% of complete TM cases.
• While steroids are sometimes administered over the first several days of illness to decrease inflammation, there is no cure for TM and treatment is largely supportive in nature. 

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• Patients with multiple sclerosis (MS), the most common autoimmune, inflammatory, demyelinating neurological condition, often present to  the emergency department with their first episode of symptoms and for treatment of future exacerbations.
• While the diagnosis of MS is ultimately made based on clinical findings such as visual abnormalities, sensory and motor complaints, gait abnormalities, and fatigue, use of brain MRI and cerebrospinal fluid (CSF) studies may be helpful in making the diagnosis.
• Brain MRI findings that are suggestive of MS include ovoid-shaped, demyelinated plaques often situated in periventricular regions and near the corpus callosum.  Seventy to 95% of MS patients will have an abnormal brain MRI.
• CSF findings suggestive of MS include oligoclonal IgG banding and is discovered in 85 to 95% of cases.

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• Any patient presenting with an acute onset of dizziness described as a spinning sensation should be thoroughly assessed for cerebellar stroke, as these often present in such a manner, prior to assuming that the source is simple vertigo.

• Cerebellar strokes, whether due to infarct or hemorrhage, typically present with ataxic gait, abnormal Rhomberg, dysmetria with finger-to-nose and heel-to-shin testing, and nystagmus.

• In addition, the dizziness associated with cerebellar strokes should be less reproducible and extinguishable than that due to simple vertigo.

• In terms of imaging, remember that CT scanning is not the preferred radiologic modality for evaluating the cerebellum and posterior aspects of the brain; the thickness of the posterior skull tends to create significant artifact and distortion. If suspicion warrants, MRI should therefore be pursued.

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• Idiopathic Intracranial Hypertension, previously known as pseudotumor cerebri, can be treated with medications such as carbonic anhydrase inhibitors (i.e. acetazolamide), corticosteroids, indomethicin, loop diuretics, and analgesics used to treat migraine headaches.

• While removing excess cerebrospinal fluid (CSF) via lumbar puncture (LP) is sometimes considered to be an appropriate therapeutic intervention for IIH in the emergency department, it is generally not recommended for the following reasons:

             -- CSF reforms within 6 hours, making its removal short-term, unless there is a CSF leak.

             -- LP can be challenging in obese patients and uncomfortable for patients, in general.

             -- LP complications such as low pressure headaches, CSF leak, CSF infection, and intraspinal epidermoid tumors.

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• Many neurologic conditions present with motor dysfunction.  It is often helpful to distinguish these movement abnormalities in order to properly recognize and manage the disorder.
• Chorea >>> Sudden, ballistic movements.
• Athetosis >>> Writhing, repetitive movements.
• Fasiculations >>> Fine twitching of individual muscle bundles, most easily noted on the tongue.
• Dystonia >>> Sudden, tonic contractions of muscles of the tongue, neck (torticollis), back (opisthotonos), mouth, or eyes (oculogyric crisis).
• Tardive dyskinesia >>> lip smacking, chewing, and teeth grinding (early signs).

Optimal management of subarachnoid hemorrhage requires prognostic understanding and effective communication with neurology and neurosurgical consultants, as well as the patient and their family members.

It is therefore often helpful to utilize and reference the widely recognized Hunt and Hess Scale in grading symptoms of ruptured cerebral aneurysm and subarachnoid hemorrhage severity:

• Grade 1:  Asymptomatic; or minimal headache with slight nuchal rigidity.  Approximate survival rate (ASR) 70%.
• Grade 2:  Moderate to severe headache; nuchal rigidity; no neurologic deficit except cranial nerve palsy.  ASR 60%.
• Grade 3:  Drowsy; minimal neurologic deficit.  ASR 50%.
• Grade 4:  Stuporous; moderate to severe hemiparesis; possible early decerebrate rigidity and vegetative abnormality.  ASR 20%.
• Grade 5:  Deep coma; decerebrate rigidity; moribund. ASR 10%.
• Grade 6:  Death; brain dead.

For your convenience, an online Hunt and Hess Scale calculating tool can be found at:

http://www.mdcalc.com/hunt-and-hess-classification-of-subarachnoid-hemorrhage-sah

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Classic Cerebrospinal Fluid Characteristics

• Bacterial Meningitis >> Milky CSF with increased protein, decreased glucose, high WBC's, few RBC's, mildly increased opening pressure, normal % gamma globulin.

• Viral Meningitis >> Cloudy CSF with increased protein, normal glucose, increased WBC's (lymphocyte predominant), no RBC's, normal opening pressure, normal % gamma globulin.

• Herpes Simplex Encephalitis >>  Cloudy CSF with increased protein, normal glucose, increased WBC's (lymphocyte predominant), few RBC's, increased opening pressure, normal % gamma globulin.

• Subarachnoid Hemorrhage >> Yellow CSF with increased protein, normal glucose, few WBC's, inumerable RBC's, mildly increased opening pressure, normal % gamma globulin.

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• A broadly-accepted, standard definition of concussion, also known as mild traumatic brain injury (MTBI), does not exist and is still a work in progress. 

• Historically, the diagnosis of concussion has been based upon the presence of three findings:  (1) Loss of consciousness (usually for less than 30 seconds), (2) post-traumatic amnesia (usually for less than 24 hours), and (3) a Glascow Coma Scale score of 13 to 15.                  

• Today, many experts question whether loss of consciousness is inherently associated with concussion, but rather that any change in consciousness, such as that related to amnesia, suffices.  

• Patients with the following symptoms should be screened, typically with head CT, for more serious injury:  loss of/deteriorating consciousness, persistent headache, dizziness, vomiting, disorientation/confusion, seizure, and unequal pupil size.

• Treatment of concussion consists of monitoring and rest.  Symptoms usually spontaneously resolve within 3 weeks, but may persist for up to around 3 months.

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• When emergently managing stroke, be vigilant about anticipating potential complications and recognizing them with expediency, regardless of whether the patient receives tPA therapy.

• The following are associated with greater risk of developing cerebral edema and/or post-tPA hemorrhage:

              ---  High NIH Stroke Scale scores.

              ---  Large areas of infarct.

              ---  Cerebellar infarcts.

              ---  Extended time to tPA administration.

              ---  Previous stroke.

              ---  Older age.
 

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• Emergency department evaluation of diplopia is largely based on a comprehensive history and should always include the following questioning with documented findings:

1. Does the diplopia resolve by covering one eye?  (Differentiates binocular diplopia (disappears when one eye covered; most common) from monocular diplopia (persists with one eye covered; usually related to a focal, ocular problem).
2. Does the degree of diplopia change with direction of gaze and/or head position?  (Determines whether deficit related to cranial nerve innervation, helps localize associated paretic muscle).
3. Is the diplopia horizontal (i.e. two objects side by side) or vertical (i.e. two objects one on top of the other)?  (Horizontal diplopia suggests cranial nerve III or VI deficit (i.e. lateral gaze function); vertical diplopia suggests cranial nerve IV deficit (i.e. elevator or depressor gaze function).
4. Is there associated pain? (Suggests possible foreign body or extraocular muscle entrapment).
5. Was there associated trauma? (Blow-out fractures can be associated with diplopia).
6. Is there associated weakness, headache, confusion, or dizziness?  (Imaging usually indicated to rule out intracranial processes such as stroke or increased intracranial pressure).

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Chlorhexidine (CHG) has rapidly become the antiseptic of choice for most skin preparation prior to any percutaneous procedures including:

• venipuncture
• laceration repair,
• joint aspiration
• lumbar puncture???

The Chlorprep^(R) label notes: "DO NOT USE FOR LUMBAR PUNCTURE OR IN CONTACT WITH THE MENINGES" (attached)

Authors of the British Royal College of Anaesthetists 3rd National Audit Project provided some guidance for the use of chlorhexidine for spinal procedures

• Clinicians must take care to prevent CHG from reaching the CSF
  • Keep CHG away from other drugs and equipment being used
  • Allow solution to dry prior to beginning procedure
  • Avoid using solutions > 0.5% chlorhexidine
• Further comments
  • Chlorhexidine 0.5% in alcohol 70% is the optimal skin preparation for neuroaxial procedures
  • Risk of vertebral canal sepsis is greater than the very rare risk of neurotoxicity and arachnoidits from chlorhexidine
  • This is OFF-LABEL use and should be instituted formally at a departmental level with an audit process for complications

Further: Correspondance from the Journal of  Regional Anesthesia and Pain Medicine

"Dr. David Hepner published a correspondence in the April 2007 issue of Anesthesiology that stated the expert panel for Regional Anesthesia and Pain Medicine “felt strongly that although the US Food and Drug Administration has not approved chlorhexidine before lumbar puncture, it has a significant advantage over povidone iodine because of its onset, efficacy, and potency” and commented that “interestingly, povidone iodine is also not approved for lumbar puncture."

Chlorhexidine off-label use is supported in academic literature.  Due to specific labeling prohibiting use, a formal institutional policy to support such use may be indicated.

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Attachments

• 1008270020_chlorprep_instructions.pdf (293 Kb)

• When examining the hand, it is always important to document assessment of the ulnar, median, and radial nerves.
• The motor function of the hand can quickly and simply be assessed with the following examination techniques:
• Ulnar motor function >> Ask patient to first turn hand prone and spread fingers apart to a maximal distance.  Then, ask the patient to resist your attempts to squeeze the fingers together.
• Median motor function >> Ask patient to touch the distal tip of the thumb to the distal tip of the fifth finger and hold it.  Then, attempt to pull the two fingers apart and ask patient to resist.
• Radial motor function >> Ask patient to extend the wrist (i.e. as if trying to stop traffic) and push back against you attempting to push the hand into the flexed position.

• The largest and most commonly injured peripheral nerve of the upper extremity is the radial nerve.
• Radial nerve palsy presents with decreased dorsal sensation, poor extensor motor strength, and a deficit in the abduction of the arm and/or hand. The degree of disability depends on where the injury takes place along the course of the nerve and its extent.
• Patients presenting with radial nerve palsy often erroneously think that they have suffered a stroke, given the severe degree of flaccidity and functional loss that typically results.
• Emergency department management of radial nerve palsy consists of splinting the wrist in a slightly extended position, along with physical and occupational therapy, and Orthopedic/Hand follow up as needed.

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How to Perform a Median Nerve Block

• The most common emergency department indication for performing median nerve blocks is to anesthetize its hand distribution (i.e. volar surface of hand) for pain control and/or to perform procedures such as laceration repair and dislocation reductions.
• The median nerve is located at the proximal flexor crease of the wrist, between the palmaris longus (PL) and flexor carpi radialis (FCR) tendons.  The FCR lies radial to the PL tendon.
• Use a 25 or 27 gauge needle, inserted to a depth of 1 cm, to inject 3-5 mL of plain lidocaine proximal to the distal wrist flexor crease, just ulnar to the PL tendon.
• If the PL tendon is absent, as is the case in 25% of people, direct the needle in line with the ring finger.
• If distal paresthesias result, withdraw and reposition the needle as this suggests that the median nerve was directly struck, which should be avoided.

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• Ulnar nerve blocks are relatively easy to perform and excellent for anesthetizing the ulnar nerve distribution, particularly of the hand.

• Ulnar nerve blocks can be performed at the level of the wrist (dorsal or volar side) or at the elbow.  Volar side blocks at the wrist tend to be easier to perform and associated with less risk. 

• Using a 27 gauge needle, infiltrate 2 to 3 mL's of lidocaine between the flexor carpi ulnaris tendon and the distal-most aspect of the ulnar bone.  The needle should be inserted 1 to 2 cm's at about a 40 degree angle, at the proximal-most wrist crease.

• Do not puncture the actual ulnar nerve or the ulnar artery.  Should needle insertion cause distal hand paresthesias or blood withdrawal, do not inject and immediately remove the needle, as this suggests that the ulnar nerve or artery was struck, respectively.  The objective is to allow the lidocaine to infiltrate into the nerve, not to inject it directly into the nerve.

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• When examining the hand, care should be taken to thoroughly assess both the sensory and motor function on both the dorsal and palmar surfaces.

• The dermatomes of the hand provide sensation and are comprised of the ulnar, median, and radial nerves (see diagram below).

• (1) Light touch, (2) sharp touch (i.e. pinprick), (3) temperature, (4) propioception (joint position sense), (5) vibration, and (6) 2-point discrimination in the following nerve distributions should be assessed:

              --  ulnar nerve >>> supplies palmar surface and dorsal tips of little finger and medial half of ring finger, including

                   adjacent parts of hand.

              --  median nerve >>> supplies palmar and dorsal aspects of thumb, index finger, middle finger, and lateral half

                   of ring finger, including adjacent parts of hand.

              --  radial nerve >>> supplies most of dorsal surface of hand.

• Cervicogenic headaches are a syndrome of chronic, hemicranial pain that is referred to the head from bony structures or soft tissue of the neck.
• Adequate treatment of these headaches is often difficult to achieve, particularly from the emergency department, as a multi-faceted approach including pharmacologic, physical, anesthetic nerve block, psychological and sometimes surgical therapy, is often required.
• The emergency physician may prescribe simple agents such as acetaminophen and ibuprofen, with or without muscle relaxants to treat cervicogenic headaches.
• When close follow up is ensured, low doses of tricyclic anti-depressants or anti-epileptics such as gabapentin, divalproex sodium, carbamazepine, and topiramate may be utilized; while these are not FDA approved for the treatment of cervicogenic headaches, they have been shown to be effective for some headache types and neurogenic pain syndromes.

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