UMEM Educational Pearls - Neurology

Sunset Eye Sign

• The "sunset eye sign" can be seen in patients with increased intracranial pressure related to obstructive hydrocephalus or shunt malfunction.
• It describes an up-gaze paresis caused by compression of the dorsal midbrain.
• The lower portion of the pupil may be covered by the lower eyelid, appearing like a setting sun.

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• Cerebral venous thrombosis (CVT) is a rare but potentially life-threatening disease.
• Mortality in CVT is largely attributed to herniation.
• The diagnosis of CVT is made on the basis of clinical presentation and imaging studies.
• When you are concerned about CVT in a patient, which neuroimaging modality should you obtain?  CT or MRI?
• Non-contrast CT
  • Often the first neuroimaging obtained as it can evaluate for other processes such as cerebral infarct, intracranial hemorrhage, and cerebral edema.
  • Dense delta sign, dense clot sign and cord sign all refer to hyperattenuation of the clot. 
  • However, these findings are only seen in 20-25% of cases and disappear within 1-2 weeks.
• MRI
  • Clot appears hyperintense in the subacute phase.
  • In the acute phase, clot can mimic normal venous flow signal and result in potential diagnostic error.
• CT venography
  • Detailed depiction of cerebral venous system.
  • Timing of contrast bolus affect quality of evaluation.
  • Reconstruction may be difficult to subtract all of the adjacent bone.
• MR venography (MRV)
  • Unenhanced time-of-flight (TOF) MR venography has excellent sensitivity to slow flow.  It is useful in detection of large occlusions (e.g. jugular venous thrombosis), but susceptible to flow artifacts.
  • Contrast enhanced MR venography improves visualization of small vessels, thus preferred to TOF MR venography.

Bottom Line:  CT venography is good for diagnosing CVT, but MRI/MRV is superior for detection of isolated cortical venous thromboses and assessing parenchymal damage.

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Airway management is an integral part of caring of critically ill patients, but is there anything that should be done differently in the neurologically injured patient?

• Injured brains are particularly sensitive to hypoxia. Avoid it by appropriate positioning and preoxygenation.
• Consider fentanyl and/or ketamine for sedation for RSI, as fentanyl can blunt the hemodynamic response to intubation, while ketamine is hemodynamically neutral and safe.
• Consider Esmolol (1.5mg/kg) prior to intubation to prevent sympathomimetic surge during intubation in the absence of multiple injuries.
• There is no role for the use of a defasciculating dose of neuromuscuclar blockade during RSI

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• A recent systematic review looked at the prevalence of psychiatric disorders such as anxiety and depressive disorders in patients with traumatic brain injury (TBI).
• They found a substantial number of patients had a history of anxiety disorders (19%) or depressive disorders (13%) prior to their TBI.
• In the first year after TBI, pooled prevalence of anxiety and depressive disorders increased to 21% and 17%.
• Prevalence continued to increase over time, with longterm prevalence of anxiety and depressive disorders of 36% and 43%.
• Females, those without employment, and those with a history of psychiatric disorders or substance abuse prior to TBI were at higher risk for anxiety or depressive disorders following TBI.

Bottom Line: 

• Early recognition and treatment of psychiatric disorders in patients after TBI may improve their outcome, psychosocial functioning and health-related quality of life. 
• Thus we should consider providing appropriate discharge instructions that include psychiatric resources for patients after TBI.

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HSV infection of the CNS is one of few treatable viral diseases. HSV encephalitis of older children and adults is almost always caused by herpes simplex virus type 1 (HSV-1), and in individuals older than 20, is due to HSV reactivation.

Temporal lobe localization is characteristic for HSV encephalitis in individuals older than 3 months, and is responsible for its characteristic presentation, namely bizarre behavior and expressive aphasia.

CSF analysis will usually reveal an elevated protein level, and a lymphocytic cellular predominance.

CSF protein concentration is a function of disease duration, and will continue to rise even with administration of treatment (acyclovir) and may remain elevated after the completion of therapy.

5% of CSF samples will be totally normal, and the diagnosis will only be revealed with positive PCR detection of viral DNA in the CSF, which is the gold standard for diagnosis.

The sensitivity of MRI is similar to CSF analysis, with 5% of patients with HSV encephalitis having a normal MRI on presentation, and subsequently developing abnormalities.

Of note, HSV-2 tends to cause aseptic meningitis rather than encephalitis in adults, and has a benign course.

Bottom Line? Keep a high index of suspicion for HSV encephalitis, and treat the patient empirically despite a normal CSF/MRI pending PCR results.

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• The NIH Stroke Scale (NIHSS) is a widely used scale in assessing neurological deficits in stroke patients.
• It is a useful communication tool and is accurate in predicting clinical outcomes.
• However, it has been critiqued for its complexity and potential poor interrater reliability of certain items within the scale.
• Prior studies have suggested modifying or shortening the scale to 11, 8 or 5 items for use in stroke clinical trials or the prehospital setting.^1,2,3

A recent study compared the original NIHSS with the shortened 11, 8, and 5 item versions.⁴

• They found the original NIHSS has higher discriminatory value and responsiveness to change as well as improved ability to predict clinical outcomes than shortened versions.

Bottom Line: The original 15-item NIHSS should still be used to evaluate patients’ stroke severity.

The reliability of the NIHSS has been found to improve with personal and videotaped training.

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Ketamine has been the drug du jour for everything from agitation to pain, but status epilepticus?

Looking at the pathophysiology of seizures, they occur due to an imbalance between excitatory mechanisms (through glutamate at the NMDA receptors) and inibitory mechanisms (at GABA receptors). The mainstay for seizure treatment has been mostly potentiation of the inhibitory mechanisms, but why not inhibit the excitatory mechanisms at the NMDA receptors?

Ketamine is the only NMDA antagonist that has been investigated for refractory status epilepticus, mostly in retrospective small series, with only 3 prospective cohort studies, totaling to 162 patients (110 adults and 52 pediatrics). Variable results were recorded, from studies with complete response in all patients to complete treatment failure, with a total of 56.5% of the adult patients having electrographic response. The optimal bolus dose appears to be 1.5-4.5 mg/kg, with an infusion of up to 10 mg/kg/hour.

Bottom Line? Consider using ketamine in patients who are in refractory status - after benzodiazepines, a 2nd line agent (such as fosphenytoin, valproic acid or levetiracetam) and IV anesthetics have failed.

(NMDA: N-methyl-D-aspartate, GABA: -aminobutyric acid)

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Last month we discussed causes of serotonin syndrome including common ED medications such as cyclobenzaprine (Flexeril), tramadol (Ultram), metoclopramide (Reglan), and ondansetron (Zofran).

Let’s conclude this series and discuss how to treat serotonin syndrome:

• Treatment of serotonin syndrome is mainly supportive.
• Discontinuation of all serotonergic agents is crucial, and may be all that's needed in mild cases.
• In moderate to severe cases, use benzodiazepines and titrate to patient sedation and normalization of vital signs.
  • Avoid droperidol and haloperidol due to their anticholinergic properties that inhibit sweating and dissipation of body heat.
  • Caution if using antipsychotics as neuroleptic malignant syndrome can be misdiagnosed as serotonin syndrome.
• Severely intoxicated patients may exhibit autonomic instability with large and rapid changes in blood pressure and heart rate.
  • This should be managed with short-acting agents, such as esmolol or nicardipine.  
• Aggressive control of hyperthermia associated with serotonin syndrome can potentially minimize severe complications such as seizures, coma, DIC, and metabolic acidosis.
  • There is a limited role for antipyretics as the mechanism is due to muscle tone rather than central thermoregulation.
  • In cases of uncontrollable hyperthermia, intubation and paralytics may be required.
• Cyproheptadine is an antihistamine with anti-serotonergic properties that should be used if no significant response to supportive measures.
  • Adult dosing is 12 mg PO followed by 2 mg every 2 hours if symptomatic. Max 32 mg in 24 hours.
• A case series reported the use of dexmedetomidine for the treatment of refractory serotonin syndrome.

This concludes our 3-part series on serotonin syndrome!

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Last month we discussed symptoms of serotonin syndrome and its diagnosis by the Hunter Criteria. Let's move on to what causes serotonin syndrome.

Serotonin Syndrome - What Causes It?

• Serotonin syndrome is not an idiopathic drug reaction, but the result of excess serotonin in the nervous system.
• It is classically associated with adminstration of two serotonergic agents, but it can occur after initiation of a single agent or increasing the dose of a serotonergic agent in individuals who are particularly sensitive to serotonin.
• Although selective serotonin reuptake inhibitors (SSRIs) are most commonly implicated, there are other medications encountered in the Emergency Department that can also play a role in serotonin syndrome.

• There are also reports of serotonin syndrome occuring with methadone, trazodone, and metaxalone (Skelaxin).
• Serotonin syndrome is often under-recognized if the symptoms are not severe.  Thus a thorough medication history is important in its purely clinical diagnosis.

** Stay tuned for the conclusion on management of serotonin syndrome **

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A thunderclap headache is defined as a very severe headache that reaches its maximum intensity within 1 minute.

One of the most common causes (and the one associated with this buzzword on board questions!) is subarachnoid hemorrhage, but what else can cause a it?

- Reversible cerebral vasoconstriction syndrome (RCVS): suggested by recurrent thunderclap headaches (2-10) over 1 to 2 weeks. Normal CT and LP, with vasoconstriction on angiography. Can lead to SAH, ICH or ischemic stroke.

- Cervical artery dissection

- Cerebral venous sinus thrombosis

- Spontaneous intracranial hypotension: characterized by orthostatic HAs and auditory muffling.

- Intracerebral hemorrhage

- “Primary”: a diagnosis of exclusion

Bottom line? All patients with thunderclap HA should have a stat head CT with no contrast, then have SAH excluded with an LP, CTA or MRI/MRA. Just because you excluded SAH in a patient with thunderclap headache does not mean you’re done with the emergency workup. 

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Serotonin Syndrome - What is It?

• Potentially life-threatening condition associated with increased serotonergic activity in the CNS.
• Selective serotonin reuptake inhibitors (SSRIs) are the most commonly implicated class of medications.  However, other medications can also be involved.
• It is a clinical diagnosis!
• Classic triad: mental status change, autonomic hyperactivity, and neuromuscular abnormalities
  • Mental status change - anxiety, agitation, restlessness, disorientation
  • Autonomic hyperactivity - diaphoresis, tachycardia, hypertension, hyperthermia, nausea, vomiting, diarrhea
  • Neuromuscular abnormalities - tremor, muscle rigidity, myoclonus, hyperreflexia, clonus, Babinski sign (abnormal plantar reflex)
• Hunter Criteria is the most accurate diagnostic rule:
  • Serotonergic agent + one of the following:
    • Spontaneous clonus
    • Inducible clonus + agitation or diaphoresis
    • Ocular clonus + agitation or diaphoresis
    • Tremor + hyperreflexia
    • Hypertonia + temperature above 38C + ocular clonus or inducible clonus
• Majority of cases present within 24 hours, most within 6 hours, of a change in dose or initiation of a medication.

** Stay tuned for part 2 on what causes serotonin syndrome **

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Status migrainosus is a migraine that lasts more than 72 hours, and can be rather challenging to control. A few tips to tackle this are:

1. Adequately hydrate all patients (IV fluids are usually required, especially with severe nausea/vomiting)

2. Establish realistic expectations for the patient. A patient with chronic daily headaches will not be pain-free in the ED.

3. Use IV nonopioid medications for pain control

1^st Line:

- Dopamine Antagonists: in increasing efficacy

- Metoclopramide

- Phenothiazines: prochlorperazine, promethazine and chlorpromazine

- Butyrophenones: droperidol and haloperidol

- NSAIDs: such as Ketorolac IV or IM

2^nd Line:

- Corticosteroids: Do not treat the migraine in the ED, but prevent headache recurrence within 72 hours.

- Magnesium Sulfate: Has shown mixed efficacy. More likely to have a sustained benefit in patient with serum magnesium level of 1.3mg/dL or less.

- Valrpoic Acid: Be careful of combining it with Topiramate.

- Vasoconstrictors: Triptans, ergotamine, dihydroergotamine. Effective, but use is limited by contraindications.

- Opioids: Last resort

Neuroimaging Tip - Loss of the Insular Ribbon Sign

• Loss of the insular ribbon sign refers to loss of the gray-white differentiation of the insular cortex.
• This is an early sign of middle cerebral artery (MCA) stroke.
• The insular cortex has less collateral blood supply from the anterior cerebral artery (ACA) and posterior cerebral artery (PCA) than other portions of the MCA territory; thus making it more susceptible to ischemia.

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Given the similarity in pathophysiology, pharmacologic treatments for ischemic stroke have been modeled after those for acute myocardial infarction, such as the use of antiplatelets and thrombolytic agents. Have you ever wondered, why don't we give glycoprotein IIb/IIIa inhibitors (GPIs) as well?
A Cochrane review answers this question; GPIs increase morbidity in acute ischemic stroke (in the form of intracranial hemorrhage), with no evidence of benefit (improvement in Rankin Scale).
The systematic review looked at randomized clinical trials of GPIs in patients with ischemic stroke of 6 hours or less, alone or in combination with thrombolytics.

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Cerebrospinal Fluid (CSF) Shunts

• CSF shunts are used to manage hydrocephalus by diverting CSF from either the ventricles within the brain or the subarachnoid space around the spinal cord to another body region. (Figure 1)
• Several types of CSF shunts exist; common types are:
  • Ventriculoperitoneal shunt
  • Ventriculoatrial shunt
  • Ventriculopleural shunt
  • Lumboperitoneal shunt
• A CSF shunt consists of 3 parts:
  • An inflow catheter directly draining CSF.
  • A one-way valve mechanism regulating the amount of CSF drainage.
  • An outflow catheter directing CSF to the drainage site.
• There are 2 types of valve mechanisms:
  • Fixed pressure valves regulate CSF drainage by a predetermined pressure threshold (i.e. low, medium, high).
  • Adjustable pressure valves can be non-invasively adjusted, via specially designed magnetic tools, to set the pressure threshold.
  • Some valves include a reservoir that can be used to test shunt function or to sample CSF for laboratory studies. (Figure 2)
• Shunt-related complications include:
  • Shunt malfunction (disconnection, migration, breaks, obstruction)
  • Shunt infection / ventriculitis / meningitis
  • Over-drainage
• A special consideration for adjustable pressure valves is precaution around magnetic devices.  If a patient is undergoing a MRI, it is recommended for the valve setting to be checked and adjusted afterwards if necessary.

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What is the ICH Score?

• The most recent AHA/ASA guideline for spontaneous intracerebral hemorrhage (ICH) recommends the use of a clinical severity score for communication.
• While the NIHSS is used for ischemic stroke, its utility may be limited in ICH due to commonly depressed mental status.
• The ICH Score is the most widely used and externally validated risk stratification scale:

• An ICH Score calculator is available on MDCalc: (http://www.mdcalc.com/intracerebral-hemorrhage-ich-score/)

Take Home Point:  Communicate the severity of your ICH patient by using either the composite ICH Score or by including details such as the patient's GCS, estimated volume of ICH, presence of IVH, and supra- vs. infratentorial origin.

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We all dread performing lumbar punctures on the obese patient. The traditional standard length spinal needle (9 cm) is becoming increasingly inadequate in reaching the subdural space in our overweight society.

Abe et al developed a formula for selecting the proper needle length to reach the middle of the spinal canal from the skin using retrospective CT data from 178 patients.

Length of needle (cm) = 1+ 17 x Weight (kg)/ Height (cm)

Given the average height of the American woman (163 cm or 5’4’’) our standard length spinal needle will FAIL to reach the mid-thecal space if a woman weighs more than 170 lb (75 kg)!!!

Paul Blart Mall Cop, and King of Queens star Kevin James (5’8’’, 285 lb) would require a 13.7 cm spinal needle. This means even our long spinal needles (12.7 cm) would FAIL by 1 cm.

Note that this formula resulted in selection of needles too small (6%) and too long (31%) of the time. Abe’s linear correlation had an R value of 0.81, (p<.001)

Bottom-Line: Consider use of a long spinal needle (12.7 cm) or IR guided LP in overweight /obese patients and the above formula to guide your depth of insertion

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Are We Using the Glasgow Coma Scale Reliably?

• The Glasgow Coma Scale (GCS), first described in 1974, has been a tool used worldwide to assess and communicate the consciousness of patients with traumatic brain injury (TBI).
• There have been reports of variations in which GCS is assessed, such as differences in technique used to elicit pain and how confounding factors such as intubation are reported.
• Reith et al. conducted an international survey of 613 health care practitioners on their methodology of GCS assessment, reporting of GCS, and attitudes toward its current use in daily practice.
  • Participants included nurses, intensivists, anesthesiologists, emergency physicians, and neurosurgeons
• Some variations in applications, methodology, and reporting from the survey include:

• This survey suggests that there is a lack of standardization of GCS assessment and reporting which affects its reliability as an assessment and communication tool
• A free educational tool has been developed (http://www.glasgowcomascale.org) to provide a standardized approach to the use of GCS

Bottom line: There are variations in the application, assessment, and reporting of the GCS.  A standardized approach is needed for it to be a reliable assessment and communication tool.

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