Introduction

The term differential diagnosis means different things to different clinicians. In this text the term will be used to answer the question that all therapists should ask themselves when they are performing the initial evaluation of a patient: Does the patient present a condition that is within the scope of physical or occupational therapy practice that the clinician can treat? If the answer is no, then the clinician has two choices. The first is to continue to manage the patient to work on those issues that can be improved with physical or occupational therapy intervention AND refer the patient to another health care provider that can help identify and treat the other condition the patient may have. The other option is to refer the patient out to another health care practitioner who is capable of diagnosing and managing the presenting condition.

This initial process of differential diagnosis is performed by the clinician while doing a thorough history and neurological examination to rule out serious neurological conditions and rule in the patient’s condition. In this case, the patient likely presented with multiple “red flags,” which are signs and symptoms that act as warnings to alert the therapist to investigate further. In the case that a patient does have a serious neurological condition, therapists need to appreciate that clusters of tests or clusters of red flag signs and symptoms are most useful to identify serious neurological conditions and that the reliance on only one test or positive red flag sign or symptom is not as conclusive to the decision making process for the clinician.

Evidence has suggested that identifying clusters of several red flags improves the sensitivity or specificity of a condition. For example, Raison and colleagues found that combining asking a patient about bowel and bladder disorders and asking the patient about saddle paresthesia and identifying two positive answers to these red flags improved the specificity to 0.92 in those patients whose magnetic resonance imaging (MRI) confirmed spinal cord compression. Kollensperger and colleagues found that clustering red flags for confirming multiple system atrophy, a condition that mimics Parkinson disease, resulted in a specificity increase to 98.5%, sensitivity to 84.2%, positive predictive value to 96%, and negative predictive value of 92.7% when clustering 2 out of 6 red flag categories.

In the neurological examination, one sign or symptom that appears as a red flag does not mean that the examination is stopped and does not mean that there is complete certainty of predicting the cause; it just increases the probability of that condition. For example, an upgoing plantar response to the Babinski test as the one positive test is considered to be a reliable marker for upper motor neuron lesion. If the clinician identifies the red flag and stops the neurological examination on the patient at that point in time, the clinician might miss the other potential positive tests or signs and symptoms that would help to clarify the patient’s diagnosis. Simply stated, red flags are used as warning signs to alert the therapist to investigate further and consider the complete examination. Red flags may occur through multiple approaches that are specific to the setting. Red flags may come from questioning the patient. Yet Premkumar and colleagues recently reported that individual red flag questions were not as effective as clusters of red flag questions, albeit in patients with low back pain. Red flags may also come as objective findings or positive neurological tests. Evidence continues to build on the compilation of red flag questions and red flag objective findings and the use of clinical decision rules to assist therapists in differentiating one condition compared to another. Evidence suggests that clustering of red flag questions and tests improves the probability of the specific condition, but this has not been explored as well with neurological conditions as it has with orthopedic conditions. After the physical examination, the next step is to evaluate the results of the examination. This systematic approach helps the therapist to identify clusters of positives and thus form clinical patterns that are consistent with specific diagnoses.

The neurological examination should be performed systematically every time. When considering a direct access primary care clinic where physical therapists work, there may be an increased probability of patients coming in with serious conditions that warrant immediate referral to another health care provider. These could be potentially life threatening and include conditions such as stroke or a patient with progressive neurological system decline such as in transverse myelitis. Transverse myelitis may initially present with low back pain and paresthesias, and rapidly progress to weakness in the extremities and bowel and bladder incontinence. In many situations like this example, this may involve additional tests and measures that the patient has to undergo to rule out conditions and ultimately identify the condition. In the multiple practice settings where occupational and physical therapists work, therapists may have a variety of resources to assist in identifying conditions, such as referral sources to assist in ordering blood work or imaging for therapists who work in the hospital, emergency department, or settings that are in close proximity to a physician, nurse practitioner, or physician’s assistant. On the other side of the spectrum, many therapists have little to no resources available to them to assist in identifying conditions, such as in school settings.

In those settings that have a variety of resources, such as the ability to quickly receive blood work or imaging, therapists must form relationships across disciplines to understand how to facilitate this process and advocate for their patients. Understanding neuroanatomy and how neurological conditions present is pivotal to improving clinical decision making and facilitating the right test for the patient with a neurological condition. For example, a patient with a suspected stroke that presents at a direct access clinic may present with a specific clinical pattern that helps the therapist conclude the location of the deficit. Anterior circulation deficits may be anterior cerebral or middle cerebral artery presentations. Anterior cerebral artery strokes in a patient may present with lower extremity weakness more than upper extremity weakness, whereas middle cerebral artery strokes present with contralateral hemiparesis and speech deficits. Posterior circulatory deficits could likely be seen in a patient presenting with vertigo, dizziness, altered mental status, or visual field deficits. By knowing this, therapists can assist with imaging requests that correspond to the patient’s clinical presentation. For example, anterior circulatory strokes are easier to catch by head computed tomography (CT). Middle cerebral artery strokes are best identified with noncontrast head CT with angiography. Head CT with angiography can be used to identify diffuse atherosclerosis and has an odds ratio of 23.6 for ischemic stroke identification. CT angiography with the addition of noncontrast head CT increases the specificity to 88% and sensitivity to greater than 70%. Small lesions such as transient ischemic attacks are hard to identify on CT, with a sensitivity of only 12%. Posterior circulatory lesions require MRI to identify (sensitivity 80%, specificity 95%).

In all settings, the therapist starts with the initial examination which includes taking a thorough history, including an investigation of the patient’s medical history, presenting complaints, and a systems review ( Box 6.1 ). In terms of differentially diagnosing the patient in the outpatient setting, a review of systems ( Box 6.2 ) is done by ensuring that a questionnaire that asks about body systems is completed by the patient, and the therapist reviews these questions with the patient to make sure the patient understands. Fig. 6.1 is an example of an intake form/medical history questionnaire that includes items for systems review and review of systems. In the inpatient setting, by contrast, a systems review and review of systems is initiated by performing a chart review to investigate the patient’s medical history followed by a physical examination of the patient. For example, in a patient with a chief complaint of inability to walk secondary to a middle cerebral artery stroke, it would be important to take their vital signs, scan their integumentary system for signs and symptoms of arterial and venous compromise, as well as to perform a complete neurological examination. A review of systems is also necessary to determine which other body systems may be pathological—whether related or not to the primary diagnosis. This history and the findings of the physical examination will lead to a diagnosis that may necessitate additional tests and measures, which may include laboratory tests or imaging that the patient needs a referral to receive. Especially in the care of the patient with a neurological condition, the therapist needs to be certain of the decision of treat, treat and refer, or refer. The identification of a condition that implicates the central nervous system after the examination of the patient, when the patient is sent to the therapist with a different referring diagnosis, is important to verify as soon as possible. This will aid in recognition of a specific diagnosis and lead to a more accurate prognosis. One way to think about a systems review is that it directs the therapist on whether to investigate that system. For example, in the patient that presents with a middle cerebral artery stroke and left neglect, the therapist needs to be concerned about the integumentary system, especially of the left upper extremity if the patient has a lesion of the dorsal column medial lemniscus tract.

Example of an Intake Form/Medical History Questionnaire.

From Goodman C, Heick J and Lazaro R. Differential Diagnosis for Physical Therapists , 6th ed. St. Louis, MO: Elsevier; 2018. Reprinted with permission

The therapist organizes the history and physical examination (including tests and measures) findings into clusters, syndromes, or categories. In the neurological examination, therapists identify clusters of findings that suggest the presence of disease or an adverse drug event and warrant communication with a physician. The therapist then considers using the World Health Organization (WHO) International Classification of Functioning, Disability and Health (ICF) model to examine the influences of both internal and external factors to the patient’s health. The ICF framework classifies the health components of function and disability. The ICF framework focuses on the three perspectives that influence the patient: body, individual, and society. By reflecting on these influences, therapists can then pair outcome measures that correctly identify how these three perspectives influence the individual with a neurological condition.

Differential diagnosis: Medical screening

The Guide to Physical Therapy Practice clearly describes the therapist’s responsibility to refer patients with health concerns to other practitioners ( Fig. 6.2 ). In the practice of treating patients with neurological conditions, many times the therapist needs to refer the patient back to the physician. This usually occurs due to the patient’s sudden changes in mental and/or physical status. This may also be associated with a recent exacerbation of symptoms such as pain, weakness, numbness, dizziness, falls, or confusion. Therapists may also detect signs or symptoms not related to the patient’s primary neurological condition but instead related to a comorbidity or a medication side effect. The systems review and review of systems may reveal a need to refer the patient for a dermatological, cardiovascular, or other system involvement not related to their primary neurological condition that requires attention by a physician ( Fig. 6.3 ).

Patient/Client Management Process Showing Therapist Referring the Patient Back to the Physician.

(Modified from Umphred DA [Chair]: Diagnostic Task Force, State of California, 1996–2000., California Chapter of the American Physical Therapy Association.)

The Physical Therapist Decision Making Process.

(Reprinted from http://ww.apta.org , with permission of the American Physical Therapy Association. © 2019 American Physical Therapy Association. All rights reserved.)

As a health care professional and especially in a direct access clinic, it is the therapist’s duty to screen the patient within their scope of practice. In screening the patient the therapist may (1) identify signs and symptoms consistent with existing medical conditions, (2) identify signs and symptoms suggesting that an existing medical condition may be worsening, (3) identify neurological manifestations that suggest an acute or life-threatening crisis, and (4) identify signs and symptoms suggestive of the presence of an occult disorder or medication side effect. This medical screening has always taken place within the clinical framework of physical therapist (PT) practice, but as direct access practitioners, this screening must become more comprehensive, requiring outcome measures and documented evaluation results. Fig. 6.4 is an example of an examination scheme that leads into a clinical decision to treat the patient, to treat and refer the patient, or to refer the patient. This figure suggests referring the patient may also include the decision to refer the patient to another practitioner (e.g., dietician, social worker, clinical psychologist) for services such as wellness clinics that encourage participation in movement activities to maintain gains experienced in therapy or once the patient has reached a plateau in rehabilitation. The following material focuses on the components of this scheme most directly related to the medical screening process leading to a patient referral.

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