What neurologic lesion can be missed if a patient's gait is not acessed as part of the neurologic exam?

Medial cerebellum.

A lesion in the medial cerebellum may cause minimal impact on the bedside examination, but the patient may have profound difficulty walking, particularly with tandem gait. In patients who are nonambulatory at baseline, midline cerebellar function may be tested by having them sit on the edge of a bed, attempting to steady themselves without the use of their hands or feet.


Source

Goldstein, J. MD and Greer. D. MD "Rapid Focused Neurological Assessment in the Emergency Department and ICU" Emerg Med Clin N Am 27 (2009), 1-16