• 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%

• Cerebral aneurysms are usually not congenital, but rather often form over days, weeks, or months.  

• It is hypothesized that the critical size for rupture is smaller for newly formed aneuryms; thus, treat newly discovered aneurysms that were previously radiographically absent more proactively and cautiously.

• While hypertension and cigarette smoking are not thought to cause aneurysmal rupture, they do contribute to the problem;  Hypertensive smokers are at a 15-fold increased risk of SAH compared to non-hypertensive non-smokers.

• About 2% of the adult population have an asymptomatic cerebral aneurysm.

• Unruptured aneurysms can cause symptoms such as headache, visual acuity loss, cranial neuropathies (particularly thrid nerve palsy), pyramidal tract dysfunction, and facial pain; these are thought to be due to mass effect on the aneurysm.

• 20 to 30% of people with a cerebral aneurysm, have multiple aneurysms; Don't miss co-existing aneurysms on CTA or MRI. 

• The majority of intracranial aneurysms are located in the anterior circulation, most commonly in the Circle of Willis.

• When localizing aneurysm on CTA and MRI, common sites include: 

              ---  junction of the anterior communicating artery (ACOM) with the anterior cerebral artery (ACA)

              ---  junction of the posterior communicating artery (PCOM) with the internal carotid artery (ICA)

              ---  bifurcation of the middle cerebral artery (MCA)

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• 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.