Hemiparesis With Normal Brain Imaging: Think Spinal, Think Functional

Dr Neeraj Mnaikath ,claude.ai

Abstract

Hemiparesis with normal brain imaging presents a diagnostic challenge that frequently perplexes clinicians in critical care settings. While cerebral pathology remains the most common cause of acute hemiparesis, a subset of patients presents with convincing neurological deficits despite normal brain computed tomography (CT) and magnetic resonance imaging (MRI). This review explores the differential diagnosis of hemiparesis with normal brain imaging, emphasizing spinal cord pathology, functional neurological disorders, and evolving cerebrovascular events. We provide practical clinical pearls and diagnostic approaches to guide post-graduate trainees in critical care medicine through this challenging clinical scenario.

Keywords: Hemiparesis, spinal cord, functional neurological disorder, cervical myelopathy, cord infarct, conversion disorder

Introduction

The presentation of acute hemiparesis typically triggers an immediate neurological workup focused on cerebral pathology. However, approximately 5-10% of patients presenting with acute hemiparesis demonstrate normal brain imaging, creating a diagnostic dilemma that requires systematic clinical reasoning and expanded differential diagnosis consideration.¹ This clinical scenario demands a paradigm shift from the traditional "brain-first" approach to a more comprehensive evaluation encompassing spinal cord pathology and functional neurological disorders.

The critical care physician must navigate between the urgency of potential treatable conditions and the recognition that not all neurological presentations have structural correlates. This review provides a structured approach to evaluating hemiparesis with normal brain imaging, emphasizing time-sensitive spinal pathology and the increasingly recognized spectrum of functional neurological disorders.

Spinal Cord Pathology: The Hidden Culprit

Cervical Myelopathy

Cervical myelopathy represents one of the most important causes of hemiparesis with normal brain imaging, particularly in elderly patients or those with degenerative cervical spine disease. The pathophysiology involves compression of the cervical spinal cord, most commonly at the C3-C6 levels, leading to upper motor neuron signs that can present as apparent hemiparesis.²

Clinical Presentation Pearls:

Asymmetric presentation: Cervical myelopathy often presents with asymmetric weakness, mimicking stroke-like hemiparesis
Nurick's sign: Loss of finger dexterity and fine motor control, often preceding gross motor weakness
Inverted radial reflex: Flexion of fingers when testing brachioradialis reflex (C5-C6 pathology)
Hoffmann's sign: Positive in 80% of cases with cervical myelopathy
Spurling's test: Neck extension with lateral flexion reproducing symptoms

Diagnostic Hack:

The "10-second test" - asking patients to rapidly open and close their hands for 10 seconds. Inability to perform this task smoothly suggests cervical myelopathy, even in the absence of obvious weakness.³

Spinal Cord Infarction

Spinal cord infarction, while rare (incidence 1.2 per 100,000), can present as acute hemiparesis, particularly when involving the cervical anterior spinal artery territory. The watershed areas at C1-C3 and T1-T4 are most vulnerable.⁴

Clinical Patterns:

Anterior spinal artery syndrome: Bilateral motor weakness with preserved posterior column sensation
Unilateral presentation: Can occur with partial anterior spinal artery occlusion
Associated features: Neurogenic bladder/bowel dysfunction, sensory level

Oyster Warning:

Unlike cerebral infarction, spinal cord infarction may not show acute changes on MRI for 24-48 hours. Diffusion-weighted imaging (DWI) has limited sensitivity for acute spinal cord ischemia compared to cerebral stroke.⁵

Brown-Séquard Syndrome

Brown-Séquard syndrome results from hemisection of the spinal cord and presents with ipsilateral motor weakness and proprioceptive loss with contralateral pain and temperature sensation loss. Common causes include trauma, tumors, multiple sclerosis, and vascular malformations.

Clinical Recognition:

Ipsilateral hemiparesis: Upper motor neuron pattern
Ipsilateral loss of vibration and proprioception
Contralateral loss of pain and temperature sensation
Sensory level: Usually 2-3 dermatomes below the lesion

Functional Neurological Disorders

Functional Hemiparesis

Functional neurological disorders (FND), previously termed conversion disorders, account for approximately 16% of neurological consultations and represent the second most common cause of neurological disability after stroke.⁶ Functional hemiparesis can present convincingly and requires careful clinical assessment.

Positive Clinical Signs:

Hoover's sign: Absence of involuntary hip extension when testing contralateral hip flexion
Collapsing weakness: Give-way weakness with inconsistent effort
Dragging gait: Affected leg dragged behind rather than circumducted
Tremor entrainment: Functional tremor changes frequency with voluntary movement of unaffected limb

Diagnostic Pearls:

Incongruent examination: Weakness that doesn't follow anatomical patterns
Distractibility: Improvement in function when attention is diverted
Inconsistency: Variability in weakness during the same examination

Conversion Disorder vs. Malingering

Distinguishing between conversion disorder and malingering requires careful clinical assessment. Conversion disorder involves unconscious symptom production without intentional deception, while malingering involves conscious symptom fabrication for external gain.

Clinical Differentiators:

Onset: Conversion disorder often follows psychological stressors
La belle indifférence: Inappropriate lack of concern about symptoms (present in only 20% of cases)
Consistency: Functional symptoms may be inconsistent but not deliberately varied
Response to suggestion: Functional symptoms may improve with therapeutic suggestion

Evolving Cerebrovascular Events

Transient Ischemic Attacks (TIA)

TIA can present as fluctuating hemiparesis with normal brain imaging, particularly in the hyperacute phase. The ABCD² score helps stratify stroke risk, but normal imaging doesn't exclude high-risk TIA.⁷

Clinical Considerations:

Timing: Symptoms may resolve before imaging
Microemboli: Small emboli may not be visible on standard imaging
Perfusion deficits: May exist without structural changes
Recurrence risk: High in first 48 hours despite normal imaging

Migraine with Aura

Hemiplegic migraine can present as acute hemiparesis and may be difficult to distinguish from stroke. The International Headache Society criteria require complete reversibility of motor symptoms.⁸

Clinical Features:

Familial vs. sporadic: Genetic forms (CACNA1A, ATP1A2, SCN1A mutations)
Aura progression: Symptoms typically develop over 5-20 minutes
Recovery: Complete resolution within 24 hours
Associated symptoms: Visual aura, sensory symptoms, aphasia

Urgent Spinal Imaging Indications

When to Image the Spine Urgently

The decision to obtain urgent spinal imaging in patients with hemiparesis requires careful clinical judgment. The following clinical scenarios warrant urgent spinal MRI:

Absolute Indications:

Sensory level: Clear dermatomal sensory loss
Neurogenic bladder/bowel: Urinary retention or incontinence
Bilateral motor signs: Even if asymmetric
Neck pain with neurological deficit: Especially in trauma or cancer patients
Progressive weakness: Despite normal brain imaging

Relative Indications:

Isolated hemiparesis: In elderly patients with cervical spondylosis
Atypical presentation: Symptoms not fitting vascular territories
Risk factors: History of malignancy, anticoagulation, or recent spinal procedures
Clinical deterioration: Worsening despite normal brain imaging

Imaging Protocols

Spinal MRI Sequences:

T1-weighted: Anatomical detail, hemorrhage detection
T2-weighted: Edema, myelomalacia, CSF evaluation
STIR (Short-TI Inversion Recovery): Sensitive for cord edema
DWI: Limited utility for spinal cord ischemia but may show acute changes

Timing Considerations:

Acute presentation: Within 6 hours if suspecting cord compression
Subacute: Within 24 hours for progressive symptoms
Chronic: Elective imaging for stable symptoms

Clinical Approach and Decision-Making

Systematic Evaluation Framework

Initial Assessment:

Detailed history: Onset, progression, associated symptoms
Neurological examination: Pattern recognition, inconsistencies
Risk factor assessment: Vascular, traumatic, malignancy, psychological
Medication review: Anticoagulation, recent procedures

Diagnostic Workup:

Brain imaging: CT/MRI with DWI and perfusion if indicated
Vascular imaging: CTA/MRA if vascular cause suspected
Spinal imaging: Based on clinical indications outlined above
Laboratory studies: Inflammatory markers, vitamin B12, syphilis serology

Treatment Considerations

Acute Management:

Airway protection: If bulbar involvement suspected
Hemodynamic monitoring: Spinal shock in cord injury
Corticosteroids: Controversial in acute spinal cord injury
Anticoagulation: Contraindicated in hemorrhagic cord lesions

Specific Interventions:

Surgical decompression: Emergent for cord compression
Thrombolysis: Not indicated for spinal cord infarction
Multidisciplinary approach: Neurology, neurosurgery, psychiatry for FND

Pearls and Oysters

Clinical Pearls:

Pattern recognition: Functional hemiparesis often violates anatomical boundaries
Timing: Spinal cord symptoms may fluctuate with position or activity
Associated symptoms: Bowel/bladder dysfunction strongly suggests spinal pathology
Examination consistency: Repeat examinations may reveal inconsistencies in functional disorders

Oysters (Pitfalls):

Normal MRI: Doesn't exclude spinal cord pathology in hyperacute phase
Functional doesn't mean feigned: Avoid dismissive attitudes toward FND
Coexisting pathology: Functional symptoms can overlay organic disease
Time sensitivity: Delayed spinal decompression can result in permanent disability

Diagnostic Hacks:

Pronator drift test: Perform with eyes closed; functional weakness often improves
Heel-to-shin test: Difficult to fake; preserved in functional hemiparesis
Tandem gait: Often preserved in functional disorders
Distraction techniques: Improvement during distraction suggests functional etiology

Prognosis and Outcomes

Spinal Pathology:

Cervical myelopathy: Surgery within 6 months optimizes outcomes
Cord infarction: Variable recovery; complete lesions have poor prognosis
Traumatic cord injury: ASIA scale predicts functional recovery

Functional Disorders:

Early diagnosis: Improves outcomes and prevents chronicity
Multidisciplinary care: Neurology, psychiatry, and rehabilitation
Patient education: Understanding diagnosis reduces healthcare utilization

Future Directions

Advances in neuroimaging, including high-resolution spinal MRI and functional connectivity studies, may improve diagnostic accuracy. The development of biomarkers for functional neurological disorders remains an active area of research. Artificial intelligence applications in pattern recognition may assist in differentiating functional from organic presentations.

Conclusion

Hemiparesis with normal brain imaging requires a systematic approach that extends beyond traditional cerebrovascular evaluation. Spinal cord pathology, particularly cervical myelopathy and cord infarction, represents treatable causes that demand urgent recognition. Functional neurological disorders, while lacking structural correlates, require careful diagnosis and appropriate management to prevent chronicity and disability.

The critical care physician must maintain clinical vigilance for time-sensitive spinal pathology while developing competency in recognizing functional presentations. A collaborative approach involving neurology, neurosurgery, and psychiatry services optimizes patient outcomes in this challenging clinical scenario.

The key to successful management lies in systematic evaluation, appropriate imaging utilization, and avoiding both overinvestigation and premature diagnostic closure. As our understanding of functional neurological disorders evolves, the integration of positive diagnostic criteria with traditional exclusionary approaches will continue to improve patient care and outcomes.

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Sunday, July 13, 2025