9.2 Diagnosis: CNS Disorders

Central Nervous System Disorders on Part II

Central nervous system (CNS) diagnosis questions on the NBCE Part II examination test whether you can recognize pattern-based presentations — sudden versus gradual onset, presence or absence of sensory involvement, UMN versus LMN signs — and respond with the correct diagnosis and referral urgency. Chiropractic students are not expected to manage acute stroke or meningitis in office, but they must identify these conditions immediately and avoid inappropriate spinal manipulation when cord compression, vascular catastrophe, or active demyelination is suspected.

Cerebrovascular Accident (Stroke)

A stroke is an acute interruption of blood flow to the brain (ischemic) or bleeding into brain tissue (hemorrhagic). The American Stroke Association reports that roughly 87% of strokes are ischemic, most commonly from large-artery atherosclerosis, cardioembolism (atrial fibrillation), or small-vessel lacunar disease. Hemorrhagic strokes (intracerebral or subarachnoid) account for the remainder and carry higher early mortality.

Ischemic vs Hemorrhagic Clues

FAST mnemonic for public screening: Facial droop, Arm weakness, Speech difficulty, Time to call emergency services. In the clinic, any acute focal neurologic deficit is a stroke until proven otherwise.

Transient ischemic attack (TIA) produces identical symptoms that resolve within 24 hours (most within minutes) but still requires emergency evaluation — TIAs herald high short-term stroke risk.

Anterior vs Posterior Circulation

• Middle cerebral artery (MCA) territory: contralateral face and arm weakness > leg, aphasia (dominant hemisphere), hemineglect (non-dominant).
• Anterior cerebral artery (ACA): contralateral leg weakness > arm.
• Posterior circulation (vertebrobasilar): vertigo, diplopia, dysarthria, ataxia, crossed sensory/motor findings (face ipsilateral, body contralateral), visual field defects.

Chiropractic red flag: Acute vertigo with diplopia, dysphagia, or crossed signs suggests posterior circulation stroke, not benign paroxysmal positional vertigo — do not perform high-velocity cervical manipulation.

Multiple Sclerosis (MS)

Multiple sclerosis is a chronic autoimmune demyelinating disease of the CNS characterized by inflammation, demyelination, and gliosis disseminated in time and space (multiple episodes affecting different neurologic systems).

High-Yield MS Presentations

Relapsing-remitting MS (RRMS) is the most common course (~85% at onset). Diagnosis uses McDonald criteria (clinical attacks + MRI demonstrating lesions separated in time and space). Disease-modifying therapy is managed by neurology.

Chiropractic consideration: MS patients may benefit from conservative musculoskeletal care during remission, but manipulation during active relapse — especially cervical — requires coordination with the treating neurologist and careful assessment for myelopathic signs.

Parkinson Disease and Other Movement Disorders

Parkinson disease (PD) results from degeneration of dopaminergic neurons in the substantia nigra pars compacta, producing a classic triad:

1. Bradykinesia (required for diagnosis) — slowness of movement, reduced blink rate, micrographia
2. Resting tremor — 4–6 Hz "pill-rolling," diminishes with intentional movement
3. Rigidity — lead-pipe or cogwheel (when superimposed tremor)

Additional features: postural instability, masked facies, hypophonia, and a characteristic shuffling gait with reduced arm swing and festination (involuntary acceleration). PD tremor improves with action; essential tremor worsens with action and is bilateral without bradykinesia.

Huntington disease presents with chorea (dance-like involuntary movements), psychiatric changes, and family history (autosomal dominant). Wilson disease should be considered in a young patient with movement disorder and hepatic dysfunction.

Spinal Cord Syndromes

Spinal cord pathology produces level-defined deficits below the lesion with UMN signs (hyperreflexia, Babinski) below the level and possible LMN signs at the level of anterior horn cell involvement.

Board favorite: Brown-Séquard produces ipsilateral motor and proprioceptive loss with contralateral pain and temperature loss beginning one to two segments below the lesion because spinothalamic fibers cross shortly after entering the cord.

Amyotrophic Lateral Sclerosis (ALS)

ALS is a progressive degeneration of upper and lower motor neurons. Key features:

• Mixed UMN and LMN signs in the same limb or across limbs (e.g., fasciculations and atrophy with brisk reflexes and Babinski sign)
• Bulbar involvement — dysarthria, dysphagia, tongue fasciculations
• No sensory loss — sensory exam remains intact, distinguishing ALS from peripheral neuropathy and many cord lesions
• No bladder/bowel involvement early — unlike cauda equina or conus medullaris lesions

Prognosis is poor; riluzole and edaravone modestly slow progression. Early neurology referral is essential.

Cerebellar Disorders

Cerebellar lesions produce ipsilateral signs:

• Ataxia — wide-based, staggering gait; cannot walk heel-to-toe
• Dysmetria — past-pointing on finger-to-nose testing
• Dysdiadochokinesia — impaired rapid alternating movements
• Intention tremor — tremor worsens as target is approached
• Nystagmus — often horizontal gaze-evoked

Vestibular vs cerebellar ataxia: Vestibular vertigo is prominent with nystagmus and nausea; cerebellar ataxia is vision-independent (Romberg may be negative or mild) whereas sensory ataxia (dorsal column loss) worsens dramatically with eyes closed (positive Romberg).

Meningitis and Encephalitis (Recognition Only)

Bacterial meningitis presents with fever, severe headache, neck stiffness (nuchal rigidity), photophobia, and altered mental status. Kernig sign (pain on knee extension with hip flexed) and Brudzinski sign (hip flexion with passive neck flexion) support but do not confirm the diagnosis. This is a medical emergency — not a chiropractic management scenario.

Encephalitis adds altered consciousness, seizures, and behavioral changes to fever and headache, often with viral etiology (HSV encephalitis is treatable with acyclovir if caught early).

Chiropractic Red Flags Summary

Refer immediately or call emergency services when you encounter: acute thunderclap headache, new focal neurologic deficit, acute bilateral leg weakness or urinary retention (cauda equina), progressive gait ataxia with UMN signs, fever with neck stiffness, or suspected spinal cord injury. Document time of onset — thrombolysis and endovascular therapy for ischemic stroke are time-critical within the first hours after symptom onset.