Radiation risk of CT

 

Today we saw a 40 yo patient with symptomatic epilepsy after traumatic brain injury, who – always after a seizure – suffered through 18 CTs of his brain during the last 2 years. One of the residents rightfully asked about the quality of his eyesight and what his risk of brain cancer was.

Reminded of an excellent article in The Journal 2010 (someone downloaded the full text here) I looked up this study by the same author in order to be able to present our group some data. In essence we don’t really know much about the risk of CT and other medical radiation (such as DSA), since all our data stems from Hiroshima and Nagasaki – there is no better data.

Left with this uncertainty, we discussed the way, how ionizing radiation leads to cancer and how, faced with an uncertain risk, we can reduce the number and intensity of our scans, especially for those epilepsy patients. Maybe it helps a bit…

Fulminant demyelination – Marburg variant, ADEM, tumefactive MS and the differential

Think of a young 26 yo female patient with a bit of optic neuritis in her past and now a rapidly progressing aphasic and encephalopathic picture. MRI reveals a huge left sided frontal demyelinating lesion with open-ring enhancement. What is the differential? How do you separate abscess from lymphoma and astrocytoma and proper demyelinating lesions, such as in tumefactive MS, ADEM/Hurst? What is the role of CSF and MR spectroscopy?

Given, then, a real (but huge) demyelinating lesion, how do you proceed? You apply the neurologic step ladder:

  • Steroids
  • Plasma exchange
  • Cyclophosphamide or Rituximab

But before you give cytotoxic agents, I would require a proper biopsy. There are plenty of reasons for this – choice of the right agent, making sure you aren’t treating lymphoma or astrocytoma. There are also many case reports that justify this approach, such as this one.

There is a wonderful book called “Tough Calls in Acute Neurology”, which covers this topic better than any review article (in fact, ther are no proper reviews on this subject).

Perampanel

Roughly each one to two years, a new antiepileptic is introduced. Since only about half of them actually survives the academic (Pregabalin) and the economic (Trobalt) scrutiny of time, it might be too early to study those drugs before they have become established. On the other hand, we might be confronted with any of those drugs and then hard-pressed to decide whether to continue them or not in, say, status therapy. So we discuss the one scenario in which perampanel has actually been investigated (add-on therapy in focal epilepsy), think about how AEDs are escalated in general and then use the drug information as well as a recent article to understand possible places for this new drug in our approach to epilepsy (and maybe status). This all with the caveat that Fycompa might actually be turned down by the GBA (a german institution that regulates reimbursement). 

Blink reflex

Starting with a patient with probable Fisher syndrome, we discuss the various ways to electrically image the brainstem. Here is what we came up with (there are other tests for research purposes, but this is what we routinely can or should be able to do):

  • Blink reflex
  • AEP
  • Calorics or rotating chair, or better: quantitative Halmagyi
  • VEMPs (we don’t do these, but they are easy to perform)
  • of course: long tracts (SEP, MEP)

We plough throught the neuroanatomy of the blink reflex, it’s technical aspects and various lesions with their typical and atypical blink reflex pathologies.

The blink reflex used to be an issue in the seventies and eighties, then with MRI we rediscovered it’s localizing potential (as opposed to – say – the masseter reflex). But it is really only useful if the MRI is negative, i.e., in those MRI-negative strokes and inflammatory lesions as well as cranial neuropathies. In the case of the latter I have to admit that a proper examination is often more effective than a good blink reflex.

As for references I turn to my beloved book on neurophysiology, which is now available in a new edition.

Bell’s palsy

Current articles concentrate on the therapeutic aspects of Bell’s palsy. I think that clinical management is way more complex than that. But most complex is the anatomy of the facial nerve.

We use a straightforward case of facial palsy to discuss the neuroanatomy of the seventh cranial nerve and then speak about about management problems. Here are some take home messages:

  • Symptoms: folklore has it that ipsilateral numbness is due to proprioceptive disturbance through motor dysfunction. Actually, via the sphenopalatine ganglion you can (as a virus) easily get to the ipsilateral V2 nerve fibres, so I (and MRI data) suggest that the numbness might be real.
  • Localization: research informs us that it is not too helpful to rely on history (taste disorder, hyperacusis and so on) and examination in order to distinguish idiopathic from other forms of facial paralysis. Why? Probably the examination is too unreliable and the symptoms are not prevalent enough.
  • Diagnosis: if you cannot perform an LP then you might use MEP, otherwise this test is unnecessary.
  • Tests: only if there are signs or symptoms of otitis or zoster, you need to involve an HEENT, otherwise a neurologician is enough to examine the meatus acusticus externus. Get an HIV, TPHA and lyme serology. Examine the parotis. Look for signs of Melkersson-Rosenthal-syndrome.
  • Quantify: grade Bell’s palsy by something like the House-Brackmann-score.
  • Management: incomplete (House-Brackmann I-III) can be managed by the primary care physician with a standard program as below. High grade facial paralysis requires neurological follow-up.
  • Follow-up: for severe paralysis do neurophysiological tests after 8-10d to judge prognosis (EMG, NCS).
  • Therapy for idiopathic Bell’s palsy: steroids (probably high dose is better than low dose as in vestibular neuritis) – start iv, switch to po on discharge. Antivirals aren’t necessary (as in vestibular neuritis). Eye care is important. Physiotherapy is probably as effective as self treatment – we use a standard set of exercise sheets.