Hemiplegia is the complete and total loss of voluntary movement on one side of the body, representing the most severe end of the unilateral motor deficit spectrum. It results from an interruption of the corticospinal (pyramidal) tract at any point from the motor cortex through the internal capsule, brainstem, or spinal cord, with weakness occurring contralateral to the lesion above the decussation of the medullary pyramids. In the acute phase, hemiplegia typically presents as flaccid (hypotonia, areflexia, loss of all movement) due to spinal shock. Over days to weeks, it evolves into spastic hemiplegia (hypertonia, hyperreflexia, clasp-knife rigidity, Babinski sign, clonus) as upper motor neuron release phenomena emerge. It differs from hemiparesis only in degree — hemiplegia = zero voluntary movement; hemiparesis = some voluntary movement preserved. Stroke is the most common cause, but hemiplegia also results from traumatic brain injury, brain tumors, cerebral palsy (a leading cause in children), demyelinating disease, and CNS infections. In ICD-10-CM, hemiplegia and hemiparesis are deliberately classified together under the same codes (G81.xx, I69.x5x), recognizing the clinical continuum between them.
Literally: “a striking of half [the body]” — evoking the sudden, blow-like onset of complete one-sided paralysis, as in stroke. The Greek plēgē is also the root of the word “apoplexy,” the historical term for stroke.
Key distinction from hemiparesis:-plegia (complete paralysis) vs. -paresis (partial weakness). The same -plegia root appears in paraplegia, quadriplegia, diplegia, and monoplegia.
🔀 ALIASES / ALTERNATE TERMS
Hemiparalysis — older synonym; rarely used in modern clinical documentation
Brunnstrom stages — motor recovery stages post-stroke hemiplegia (I-VI)
Fugl-Meyer Assessment — quantitative motor recovery scale
Constraint-induced movement therapy (CIMT) — intensive upper extremity rehabilitation
Ankle-foot orthosis (AFO) — common assistive device for hemiplegic gait (foot drop)
Spasticity — major complication of chronic hemiplegia; treated with baclofen, botulinum toxin
CODING CORNER
### 🏥 ICD-10-CM CODES
Critical Note: ICD-10-CM category G81 is titled “Hemiplegia and hemiparesis” — both conditions share every code in this category. The documentation of hemiplegia vs. hemiparesis does not change the code; both map to the same codes. The 4th character specifies type (flaccid, spastic, unspecified) and the 5th character specifies side and dominance.
⚠️ Coding Note: The single most important distinction for inpatient coders: G81.xx is used when hemiplegia is NOT a sequela of cerebrovascular disease (e.g., cerebral palsy, TBI, tumor, MS, Todd’s paralysis). When it IS a documented sequela of stroke or intracranial hemorrhage, use the I69.X5X codes exclusively — do not code both G81 and I69.x5x for the same condition. The I69.X5X codes are CC (Complication/Comorbidity) under MS-DRG and significantly impact DRG weight. The flaccid vs. spastic distinction in G81 matters for specificity — flaccid (G81.0x) reflects the acute/LMN phase while spastic (G81.1x) reflects the chronic/UMN recovery phase; query the physician when this is not specified. As always, document and code laterality and dominance to the highest specificity possible — unspecified codes (ending in 0 or 9) should be used only as a last resort.
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