My elderly patient is scheduled to undergo elective surgery? Is there an objective “stress test for the brain” that may predict postoperative delirium?

Possibly, in the near future! Although the pathophysiology of postoperative delirium (POD) is not fully understood, a recently proposed conceptual model of delirium may provide a basis for preoperative neurophysiologic testing1.

According to this model, delirium is a “consequence of the breakdown in brain network dynamics” precipitated by insults or stressors (eg, surgery) in persons with low brain resilience ie, low connectivity between brain regions and/or deficient neuroplasticity (the ability of brain to reorganize itself by forming new neural connections).  

As expected,  patients with strong baseline connectivity and optimal neuroplasticity would not be expected to have POD, whereas those with weakened connectivity (eg baseline cognitive dysfunction) and/or suboptimal neuroplasticity (eg due to aging) may be at higher risk. Transcranial magnetic stimulation (TMS)  is considered a powerful tool that measures the connectivity and plasticity of the brain through induced perturbation.  When applied in repetitive trains, TMS produces changes in cortical excitability that can be measured using electromyography and EEG,  and is thought to have the ability to assess neuroplasticity 2. If proven effective in predicting POD, it could revolutionize preoperative risk assessment in the elderly! Stay tuned!

 

Reference

  1. Shafi MM, Santarnecchi E, Fong TG, et al. Advancing the neurophysiological understanding of delirium. J Am Geriatr Soc 2017. DOI:10.1111/jgs.14748.
  2. Pascual-Leone A, Freitas C, Oberman L, et al. Characterizing brain cortical plasticity and network dynamics across the age-span in health and disease with TMS-EEG and TMS-fMRI. Brain Topogr 2011, 24:302-15.
My elderly patient is scheduled to undergo elective surgery? Is there an objective “stress test for the brain” that may predict postoperative delirium?

How should I interpret a positive Treponema serology by enzyme immunoassay (EIA) in my elderly patient with dementia?

The treponema-specific antibody tests by EIA (e.g. Trep-Sure) are much more sensitive and specific than RPR, especially during the primary and late stages of syphilis (1).  A positive EIA treponema-specific test should be followed by an RPR to better assess disease activity.  If the RPR is positive, further evaluation for neurosyphilis with lumbar puncture may be necessary. If the RPR is negative, a more specific treponema test (e.g. fluorescent tryponemal antibody [FTA], or  Treponema pallidum particle agglutination[TP-PA]) should be performed for confirmation(1).  Remember also that serum RPR may be negative in about 30% of patients with neurosyphilis (2); so a negative serum RPR does not rule out neurosyphilis.

1. Binnicker MJ, Jespersen DJ, Rollins LO. Treponema-specific tests for serodiagnosis of syphilis: comparative evaluation of seven assays 2011;49:1313-1317.

2. Whitefield SG, Everett As, Rein MF. Case 32-1991;tests for neurosyphilis. N Engl J Med 1992;326:1434..

How should I interpret a positive Treponema serology by enzyme immunoassay (EIA) in my elderly patient with dementia?