13.5 Diagnostic Procedures: Imaging, MSK Ultrasound, Urodynamics & Neuropsych Assessment
Key Takeaways
- Diagnostic procedures in the foundational domain include gait analysis (Chapter 2.9), medical imaging, musculoskeletal ultrasound, urodynamics, neuropsychological evaluation, and laboratory studies—each selected by clinical question.
- Imaging modalities differ by tissue: MRI best for soft tissue, spinal cord, and marrow; CT for bone detail and acute hemorrhage; radiographs for fractures and alignment; bone scan/SPECT for occult fracture/osteomyelitis; PET for oncologic/metabolic imaging.
- Musculoskeletal ultrasound dynamically evaluates tendons, ligaments, and nerves (e.g., carpal tunnel median nerve cross-sectional area, rotator cuff tears) and guides injections without ionizing radiation.
- Urodynamics characterizes bladder dysfunction (detrusor overactivity, poor compliance, detrusor-sphincter dyssynergia) guiding therapy; neuropsychological assessment quantifies cognition and guides rehabilitation planning after brain injury/stroke.
Diagnostic Procedures: Imaging, MSK Ultrasound, Urodynamics & Neuropsych Assessment
Diagnostic procedures form a Domain A sub-area (gait analysis is in Section 2.9). The physiatrist selects and interprets imaging, ultrasound, urodynamics, and neuropsychological testing to clarify diagnoses and direct rehabilitation.
Medical Imaging Selection
| Modality | Best For | Rehab Use Example | Limitation |
|---|---|---|---|
| Radiograph | Bone cortex, alignment, fractures | Fracture follow-up, prosthesis alignment | Poor soft-tissue detail |
| CT | Bone detail, acute hemorrhage, complex fractures | Cervical spine fracture, heterotopic ossification extent | Radiation; metal artifact |
| MRI | Soft tissue, spinal cord, marrow, tendons/ligaments | Spinal cord compression, rotator cuff, demyelinating plaques | Contraindications (some implants), cost |
| Bone scan/SPECT | Occult fracture, osteomyelitis, metastases | Stress fracture, complex regional pain syndrome | Nonspecific uptake |
| DEXA | Bone mineral density | Osteoporosis screening/monitoring | Bone density only |
| Fluoroscopy | Real-time procedures | Spine injections (see pain chapter) | Radiation, operator-dependent |
| US | Tendon/ligament/nerve dynamic, fluid | Tendon tears, effusions, guided injection | Operator-dependent; limited for deep structures |
Musculoskeletal Ultrasound
MSK ultrasound dynamically images tendons, ligaments, muscles, joints, and peripheral nerves. High-yield applications:
- Rotator cuff: full- vs partial-thickness supraspinatus tears, tendinosis, bursal fluid.
- Carpal tunnel: median nerve cross-sectional area at the wrist (>10-12 mm² supports CTS).
- Lateral epicondyle: tendon thickening, neovascularity, tears.
- Achilles and patellar tendons: tendinosis, neovascularity, partial tears.
- Joint effusions and guided injections/aspirations.
Advantages include dynamic real-time assessment, no ionizing radiation, and image-guided interventions; limitations are operator dependence and limited penetration/deep-structure assessment. The AANEM and ACR acknowledge MSK US in physiatric and rheumatologic practice.
Urodynamics
Urodynamic studies characterize lower urinary tract function in neurogenic and non-neurogenic bladder dysfunction.
| Component | Measures / Detects |
|---|---|
| Uroflowmetry | Peak flow rate, voiding pattern |
| Cystometry (CMG) | Bladder sensation, capacity, compliance, detrusor overactivity |
| Pressure-flow study | Bladder outlet obstruction vs impaired contractility |
| Leak point pressures | Detrusor leak point (SCI above T6 risk high pressures), abdominal leak point (stress incontinence) |
| EMG of external sphincter | Detrusor-sphincter dyssynergia (DSD; suprasacral SCI) |
Findings guide therapy: detrusor overactivity → anticholinergics/beta-3 agonists/botulinum; DSD with high pressures → intermittent catheterization ± alpha-blockers; low compliance → early intervention to protect upper tracts (renal function monitoring, low bladder storage pressures).
Neuropsychological Assessment
Neuropsychological evaluation uses standardized batteries to quantify cognitive domains (attention, memory, language, executive function, visuospatial, processing speed) and emotional functioning after TBI, stroke, tumor, or neurodegenerative disease. It informs rehabilitation planning, return-to-work/school, capacity decisions, and outcome measurement. Functional scales (FIM, Glasgow Outcome Scale, Rancho levels) complement—but do not replace—formal neuropsychological testing. Neuropsychologists also help distinguish depression/pseudodementia from genuine dementia and identify functional cognitive overlay.
Laboratory Studies & Integration
Common labs support rehab diagnoses: CBC/anemia (exercise tolerance), renal function (NSAID/contrast dosing), vitamin D/B12, thyroid (myopathy/fatigue), HbA1c (wound healing), inflammatory markers (rheumatologic disease), and drug levels. The physiatrist integrates imaging, ultrasound, urodynamics, neuropsychological testing, and labs with the clinical exam to build a coherent rehabilitation plan.
Imaging Safety & Contrast Considerations
Imaging choice weighs diagnostic yield against risk: CT ionizing radiation (cumulative cancer risk, dose-reduction in children/pregnancy), MRI gadolinium retention (kidney function-dependent NSF risk), and contrast allergy/renal function. The physiatrist selects the lowest-yield-sufficient study, coordinates renal function and allergy precautions, and recognizes implants (pacemakers, clips, neurostimulators) that constrain MRI. Pre-procedural contrast protocols and metformin management around iodinated contrast are recurring exam points.
Electrodiagnosis as a Diagnostic Adjunct
While detailed electrodiagnosis is in Chapter 5, the foundational diagnostic-procedures domain includes recognizing when EMG/NCS complement imaging: radiculopathy (EMG myotomal pattern vs MRI structural), entrapment neuropathy (localizing conduction slowing), and distinguishing neurogenic from vascular TOS. The physiatrist sequences non-invasive tests (imaging, ultrasound, urodynamics, neuropsych) before invasive ones and integrates them with the clinical exam.
Urodynamics Interpretation Pearls
| Pattern | Finding | Implication |
|---|---|---|
| Detrusor overactivity | Uninhibited contractions during filling | Urge/neurogenic; anticholinergic/beta-3/botulinum |
| Low compliance | High pressure at low volume | Upper-tract risk; reduce storage pressure early |
| Detrusor-sphincter dyssynergia | EMG activity during detrusor contraction | Suprasacral SCI; intermittent catheterization ± alpha-blocker |
| Outlet obstruction | High detrusor pressure, low flow | BPH, stricture; alpha-blocker/surgery |
| Areflexic bladder | No detrusor contraction | Sacral/conus; clean intermittent catheterization |
Low-compliance bladders with high storage pressures risk upper-tract deterioration; detrusor leak point pressures >40 cm H2O historically flagged upper-tract risk, prompting early intervention. The physiatrist integrates urodynamics with renal function surveillance (creatinine, upper-tract imaging) for lifelong neurogenic bladder management.
Neuropsychology: Application & Limitations
Neuropsychological testing is most informative in stable (subacute-to-chronic) phases; acute confusional states and fluctuating deficits limit interpretability. Findings guide diagnosis (differential of dementia vs depression vs FND cognitive overlay), rehabilitation planning (strengths/weaknesses, compensatory strategies), capacity/legal questions, return to work/school, and outcome measurement. Limitations include practice effects with repeat testing, cultural/educational test bias, and effort/cognition interaction—formal effort testing is part of contemporary assessment. The physiatrist refers judiciously and integrates results into the multidisciplinary plan rather than treating the report in isolation.
Which imaging modality is best for evaluating a suspected acute spinal cord compression in a myelopathic patient?
Which MSK ultrasound finding best supports a diagnosis of carpal tunnel syndrome?
Urodynamic EMG of the external urethral sphincter in a patient with a suprasacral spinal cord injury most commonly demonstrates which pattern?
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