American Board of Psychiatry and Neurology (ABPN) Practice Exam

A 29-year-old woman presents with rapidly progressive bilateral leg weakness and had a bout of diarrhea prior to her symptoms. Which finding would not be likely on testing?

1. Diminished deep tendon reflexes

2. High cell count with absent protein in CSF

3. Conduction block and prolonged F-wave latencies

4. Positive Campylobacter jejuni antibody serology

The correct answer is: High cell count with absent protein in CSF

The scenario presented describes a case suggestive of Guillain-Barré Syndrome (GBS), particularly following a gastrointestinal infection, which is commonly associated with Campylobacter jejuni. In this context, certain findings on testing are expected. A high cell count with absent protein in the cerebrospinal fluid (CSF) would not be typical for GBS. In this syndrome, the classic CSF finding is albuminocytologic dissociation, which means there is an elevated protein level with a normal white cell count. Therefore, the likely finding in the CSF would be a high protein concentration with normal white blood cell count, rather than a high cell count with absent protein. On the other hand, diminished deep tendon reflexes are common in GBS due to the progression of motor neuropathy resulting from demyelination. These reflexes are often reduced as the condition affects the peripheral nervous system. Conduction block and prolonged F-wave latencies are indicative of demyelination, which is a key feature in GBS. These electrophysiological findings help confirm the diagnosis of the condition as they show the abnormalities in nerve conduction. Additionally, positive serology for Campylobacter jejuni antibodies reinforces the link between the recent gastrointestinal illness and the