Psychogenic Neurologic Deficits

The Neurologist’s Role

Even in the face of flagrant psychogenic signs, neurologists generally test for neurologic illnesses that might explain a patient’s symptoms, especially ones that would be serious or life-threatening. Although in many cases, simply observing the course of the illness proves the most reliable way of making a diagnosis, at the initial consultation, neurologists tend to request extensive evaluations to obtain evidence for the presence or absence of a disease. They do not specify whether a patient’s symptoms and signs are of conscious or unconscious origin, subsuming both under the category of psychogenic disorders. Moreover, for them, factitious disorder, malingering, and embellishment (exaggeration of a known neurologic deficit) all fall under the umbrella term “psychogenic disorder.” For example, they do not differentiate between a person with “blindness” as a manifestation of an unconscious conflict and someone mimicking blindness to gain insurance money. Neurologists usually use the term “psychogenic” rather than, as several organizations have suggested, “functional.” Reflecting that preference, this book uses “psychogenic” because it is clear and encompasses deliberate as well as unconscious motivation.

Within the framework of this potential oversimplification, neurologists reliably separate psychogenic disorders from ones that have a physiologic basis. They also recognize when patients have mixtures of neurologic and psychogenic deficits, disproportionate disabilities, and minor neurologic problems that preoccupy them.

Image-based neurologic research studies have shown physiologic changes in patients with conversion disorders. The results are neither consistent nor clinically applicable, but many suggest hypoactivation of the supplementary motor area or disconnection with centers that determine motor activity, that is, abnormally low activity in the frontal lobe.

Neurologists working with psychiatrists will probably attribute most psychogenic symptoms or deficits to Conversion Disorder (Functional Neurological Symptom Disorder) , which constitutes a category under Somatic Symptom and Related Disorders in the Diagnostic and Statistical Manual of Mental Disorders, fifth edition ( DSM-5 ). The diagnostic criteria for Conversion Disorder include one or more symptoms of altered voluntary motor or sensory function, incompatibility of the symptoms with neurologic and medical conditions, and distress or impairment in an important area of functioning. Overall, the diagnosis rests on the neurologic examination showing findings that are incompatible with disease. The diagnosis does not require physicians to uncover psychologic factors or to demonstrate that any findings are feigned. This chapter discusses several well-established psychogenic motor or sensory findings. Later chapters offer additional information concerning psychogenic nonepileptic seizures (PNES) (see Chapter 10 ), psychogenic diplopia and blindness (see Chapter 12 ), and psychogenic tremors (see Chapter 18 ).

Psychogenic Deficits

What general clues prompt a neurologist to suspect a psychogenic deficit? When a deficit violates the laws of neuroanatomy, neurologists almost always deduce that it is psychogenic. For example, if temperature sensation is preserved but pain perception is “lost,” the deficit is nonanatomic and therefore likely to be psychogenic. Likewise, tunnel vision, which clearly violates these laws, is a classic psychogenic disturbance (see Fig. 12.8 ). (One caveat in this example is that migraine sufferers sometimes experience tunnel vision as an aura [see Chapter 9 ].)

Another clue to a psychogenic basis of a deficit is a sudden onset and then a variable presence. Obviously, if someone who appears to have developed hemiparesis or paraparesis sits in a wheelchair all day but walks when unaware of being observed, neurologists conclude that the paresis is psychogenic. A clear example occurs when someone with a “seizure” momentarily “awakens” and stops convulsive activity but resumes when aware of being observed. The psychogenic nature of a deficit can sometimes be confirmed if it is reversed during an interview while under the influence of hypnosis or a powerful suggestion, such as entrainment of a psychogenic tremor (see Chapter 18 ).

Similarly, a “give-way” effort where the patient offers a brief (several seconds) exertion before returning to an apparent paretic position indicates a fluctuating effort. Likewise, in the face-hand test , a patient momentarily exerts sufficient strength to deflect their falling hand from hitting their own face ( Fig. 3.1 ).