Why localize lesions?

Discussion in 'Neurology' started by drboris, Dec 15, 2005.

  1. drboris

    drboris Senior Member
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    Hey guys,

    I really liked neuro and because of that am interested in neurology, but I don't see the point of localizing every singe lesion when it doesn't help the treatment. Who cares where the lesion is in stroke if we still can't do anything about it >3hrs? If I am wrong, then somebody please enlighten how localization helps determine treatment (if any is available).

    Thanks
     
  2. doctorlarry

    doctorlarry Member
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    A correct diagnosis in neurology is key. Localizing lesions allows you to narrow down your endless list of differentials greatly since lesions in certain locations may only be explained by certain pathologies. This may also cut down on expensive superfluous tests if you can explain the patient's presentation on one location along the neuraxis. I imagine you have heard all this during your neuro rotation ad nauseum.

    As far as stroke is concerned, they may present in so many different ways, and may mimic other pathologies. In order to treat the patient safely, we must first go through the stepwise algorithms in our mind to arrive at a correct diagnosis. Furthermore, there are different etiologies for stroke, and one should investigate all causes thoroughly. Treatment regimens will depend on it for secondary prevention, etc.
     
  3. kasimagore1

    kasimagore1 Member
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    Why localize? I'll give you an example pertaining to stroke. how do you know patient A with left arm weakness is having a stroke when he presents to you 1 hour post onset of symptoms? Without localization (as CT won't tell you jack 1 hour post ischemic stroke, unless it's a gigantic infarct w/wo hemorrhagic transformation or a head bleed). So what are you going to do? administer TPA to everyone with a left arm weakness? Localization is the KEY. Even you can't pinpoint exact location of the lesion, you can at least differentiate whether it's a problem of the cortex, subcortical area, brainstem, spinal cord, cervical plexus and roots, the peripheral nerves, neuromuscular junction, muscular lesions, or a conversion/function disorder. It will become clear when you do a neuro rotation.
     
  4. PublicHealth

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    Anyone remember the good ol' pre-imaging days when neurologists and neuropsychologists had to play "guess the lesion?" This approach should be incorporated into existing programs for educational purposes. What a great way to learn the art of diagnosis and appreciate the history of your field.
     
  5. Whodathunkit

    Whodathunkit Senior Member
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    Lawyers have made that era hard to live in these days.
     
  6. PublicHealth

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    Bah Humbug!
     
  7. Bonobo

    Bonobo Senior Member
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    Just to add two examples that I saw in the last month where localizing the lesion had an important impact on my patients' health--and I am not even on a neurology rotation yet! (And both involve strokes--obviously, it pays to localize the lesion in terms of the "neuroaxis" comparing lesions occurring in for example, the cortex vs the neuromuscular junction)

    1. An eldery woman came in with a bad headache and some nausea. A traumatic LP showed some xanthochromia, but head CT was read as negative, so she was sent to the medicine ward. I happened to do a thorough neuro exam and found a diplopia on lateral upward gaze suggesting a cranial nerve III (based on more thorough neurological examination) lesion. There was no other neurological finding, and the patient's headache was gone (she had gotten some narcotics in the ED). This diplopia, however, caused concern for a 'sentinal' bleed from an aneurysm, and after a call to neurosurgery, she was taken to the neuroICU and got an emergent cerebral angiogram. They called this negative except for some mild ICA stenosis. But knowing the neurological finding and the suggested localization, her NICU neurologist pushed them to get an MRI/MRA, and there it was: a small hemorrhage impinging on the third nerve. Guess what? She was previously on coumadin, and this of course had to be stopped. A simple, but possibly life-saving intervention based initially on neurological localization. (Of course, the astute neurologist would recognize that xanthochromia should not have been disregarded by the ED and admitting triage with simply a head CT!!)

    2. A right-handed lady in ESRD who during HD suddenly lost her speech, developed a slight left facial droop, and developed weakness in left lower extremity. Got to the ED in less than 40 min! What would you do? Head CT showed hypoattenuations in left and right corona radiata, and another in the right pons--all likely to be old infarcts per history, but it might be too early to diagnose another new stroke. Here, again, localizing the cause of her symptoms is important. On one hand, this might have been a new stroke that could benefit from tPA. On the other hand, the neurologist noted that the symptoms appeared crossed, (left Broca's area and right pre/primary motor area--or the respective white matter tracts in the lenti). His suspicion was that the lady became hypotensive during dialysis (a common condition) that led to bringing out her old strokes. Indeed, a couple hours later, the patient began to recover from these symptoms, and 1 day later (when I saw her) she was back at baseline. This changed management by simply telling HD to be more careful with her volume shifts so as to prevent acute hypotension.

    There are many other examples such as this. I think, oftentimes neurologists don't credit for their localization abilities because other doctors don't understand the process as well. It is like that nurse who wonders why you can't just give 10mg of Ambien to the fellow who can't sleep without going through their history and meds very carefully.

    I wanted to note one other MAJOR reason why localization is becoming more and more important (rather than the reverse!). Neurology/Interventional neurology/Neurosurgery now has the capability of treating patients very acutely when they have acute ICH with impending herniation and strokes. In the near future, the 30 minutes it takes to wheel a patient down to the CT scanner and take the scan (forget MRI!), might be the difference between life and death for many patients. I have seen emergent EVDs/Bolts placed before, and I suspect that emergent cerebral catherization for strokes may be on the horizon as well. In both cases, the neurological exam and powers of localization becomes the neurologist's EKG differentiating the "ST-elevation-I have to do something NOW" patient from the "yawn-another NSTEMI".

    B
     

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