Palsy is a clinical and lay synonym for paralysis or paresis — the complete or partial loss of voluntary motor function in one or more body regions — derived from Old French and representing the popular phonological reduction of the Latin paralysis; while the term is no longer used as a standalone diagnosis in modern ICD-10-CM, it is formally preserved in the names of numerous distinct clinical entities including Bell’s Palsy (G51.0), cerebral palsy (G80.0-G80.9), Erb’s palsy (P14.0), progressive supranuclear palsy (G23.1), bulbar palsy (G12.22), pseudobulbar palsy (F07.89), Saturday night palsy (radial nerve palsy, G56.30-G56.32), and peroneal nerve palsy (G57.30-G57.32). The pathophysiological mechanism underlying each palsy entity varies by eponym: Bell’s palsy involves acute inflammatory demyelination of cranial nerve VII (facial nerve) producing lower motor neuron (LMN) unilateral facial paralysis with ipsilateral forehead involvement; cerebral palsy encompasses a family of nonprogressive UMN motor disorders from perinatal brain injury; and progressive supranuclear palsy is a neurodegenerative tauopathy causing vertical gaze palsy, postural instability, bradykinesia, and executive dysfunction distinct from Parkinson’s disease. Clinically, “palsy” as a word carries the implicit connotation of weakness or partial loss rather than complete abolition of motor function — overlapping with paresis — though individual entities (e.g., complete Bell’s palsy) may involve total loss; this ambiguity is why modern surgical and neuroscience literature favors the more precise terms paralysis and paresis over “palsy” outside of named disease contexts. It is commonly confused with spasm or tremor — note the key difference: palsy/paralysis involves loss of motor output, while spasm and tremor involve excess or disordered motor output; these are physiologically opposite phenomena despite sometimes appearing together in complex movement disorders.
Greek lysis (LY-sis), from lyein (LY-ein) “to loosen, to dissolve, to release”
Noun-forming suffix — “a loosening,” “a dissolution,” “a breaking down of function”
The word entered English in the 1300s as palsy (noun), a phonological reduction of Old French paralisie (parleisie, parlesie), itself borrowed from Latin paralysis, from Greek parálysis (“disabling of the muscles, palsy”) — literally “a loosening beside [normal function]” or “a disordering of one side.” The contraction from paralysis → paralisie → palsy mirrors the same vernacular shortening seen in French and Middle English medical lay vocabulary, paralleling “dropsy” (hydrops) and “epilepsy” (epilepsia). The root lyein (“to loosen”) connects palsy to the entire -lysis root family: paralysis (para- + lysis → disordered loosening), dialysis (dia- +-lysis → separation through), hemolysis (hemo- + lysis → dissolving of blood), and catalysis (kata- + lysis → a loosening down). The prefix para- remains highly productive in neurology, appearing in paraplegia, paresthesia, paranoia, paraparesis, and paraphasia.
🔀 ALIASES / ALTERNATE TERMS
paralysis(the formal clinical and anatomical synonym for palsy; complete loss of motor function; used in modern nosology where “palsy” is reserved for named eponymic entities — e.g., G51.0 Bell’s palsy but G81.x hemiplegia, not “hemipalsy”)
Paresis(partial motor weakness; the incomplete form of palsy; “paresis” is the preferred modern term when some residual motor function is retained — e.g., hemiparesis vs. hemiplegia)
Bell’s Palsy(acute unilateral idiopathic LMN facial nerve palsy; most common cause of facial paralysis; coded G51.0; LMN = ipsilateral forehead involved, distinguishing it from central UMN “central seven” facial palsy in stroke)
Cerebral Palsy (CP)(umbrella term for a family of nonprogressive motor disorders from perinatal brain injury; subtypes coded G80.0-G80.9; not a single disease but a heterogeneous group of UMN movement disorders)
Bulbar Palsy(LMN paralysis of cranial nerves IX, X, XI, XII affecting swallowing, speech, and tongue movement; produces dysarthria, dysphagia, and tongue fasciculations; coded G12.22 progressive bulbar palsy)
Pseudobulbar Palsy(UMN-type bulbar dysfunction — spastic dysarthria, dysphagia, emotional lability/pathological crying/laughing; coded F07.89 other postconcussional/neurological behavioral disorders when pseudobulbar affect is specified)
Saturday Night Palsy / Radial Nerve Palsy(compressive radial nerve injury causing wrist drop; often from prolonged arm compression; coded G56.30 lesion of radial nerve, unspecified upper limb; G56.31 right; G56.32 left)
Peroneal Palsy / Common Fibular Nerve Palsy(compressive or traumatic injury to common peroneal nerve at fibular head; produces foot drop; coded G57.30 unspecified lower limb; G57.31 right; G57.32 left)
Facial Palsy(included in ICD-10-CM as an inclusion term under G51.0 Bell’s palsy — “facial palsy” maps directly to G51.0 unless another etiology is specified, e.g., Ramsay Hunt syndrome B02.21, or Lyme disease A69.22)
🔗 RELATED TERMS
Bell’s Palsy — the most clinically common entity using “palsy”; acute idiopathic CN VII LMN palsy; viral etiology suspected (HSV-1 reactivation); distinguishable from stroke-related central facial palsy by presence of forehead muscle involvement; coded G51.0; treated with corticosteroids ± antivirals
Facial Nerve (CN VII) — the cranial nerve whose dysfunction defines Bell’s palsy; travels through the internal auditory canal, geniculate ganglion, mastoid segment, and exits the stylomastoid foramen; the long, complex course explains multiple etiologies of facial palsy beyond Bell’s
Ramsay Hunt Syndrome — varicella-zoster virus (VZV) reactivation at the geniculate ganglion causing facial palsy + herpetic vesicles in the ear canal (herpes zoster oticus) + sensorineural hearing loss; coded B02.21; differentiated from Bell’s palsy by vesicles — important coding distinction since B02.21 is sequenced as principal when zoster is confirmed
Central Facial Palsy — UMN facial weakness from stroke or cortical lesion; forehead is spared (bilateral cortical input to dorsal facial nucleus) unlike Bell’s palsy (LMN); not separately coded — maps to the underlying stroke code + G81.x hemiplegia as applicable
Progressive Supranuclear Palsy (PSP) — neurodegenerative 4-repeat tauopathy; vertical gaze palsy is pathognomonic; differentiated from Parkinson’s disease by axial > limb rigidity, early falls, and absence of resting tremor; coded G23.1; high-dollar inpatient profee encounter
Cerebral Palsy — the most volumetrically common palsy in pediatric inpatient profee coding; nonprogressive UMN disorder from perinatal brain injury; always coded from the G80.x family — never substitute G81.x or G82.x for a CP patient; spastic diplegia (G80.1) is a CC per CMS MS-DRG
Erb’s Palsy — most common birth-related nerve injury; upper brachial plexus (C5-C6) stretch/avulsion during delivery; “waiter’s tip” posture (arm adducted, internally rotated, elbow extended, forearm pronated, wrist flexed); coded P14.0; distinguish from acquired adult brachial plexopathy G54.2
Bulbar Palsy — LMN cranial nerve IX/X/XI/XII paralysis; key differentiator from pseudobulbar palsy: bulbar = hyporeflexic/flaccid tongue with fasciculations; pseudobulbar = hyperreflexic/spastic tongue without fasciculations; both cause dysphagia and dysarthria but require different code families
Electromyography (EMG) — primary electrodiagnostic tool for evaluating nerve and muscle integrity in palsy; facial EMG coded 95867 unilateral or 95868 bilateral; limb EMG 95860-95864 and 95885-95887 with NCS; critical for predicting Bell’s palsy prognosis (Wallerian degeneration on EMG = poor prognosis)
Nerve Conduction Studies (NCS) — companion test to EMG; assesses velocity, amplitude, and latency of nerve conduction; coded 95907-95913 by number of studies; essential in distinguishing LMN palsy patterns
Facial Nerve Decompression — surgical decompression of CN VII within the temporal bone for severe Bell’s palsy with complete denervation on EMG; controversial; coded 69955; payer prior authorization typically requires EMG findings and failure of conservative management
Facial Nerve Graft — surgical nerve repair for permanent facial palsy (post-tumor, trauma); free fascia graft coded 15840; nerve graft head/neck ≤4 cm 64885, >4 cm 64886; facial nerve suture extracranial 64864
Other personality and behavioral disorders due to known physiological condition (pseudobulbar affect / emotional lability in pseudobulbar palsy — when documented as a behavioral/emotional manifestation)
🔧 COMMON CPT CODES (Palsy — Diagnosis & Management)
Therapeutic activities; direct patient contact (15 min — functional motor retraining post-palsy)
⚠️ Coding Note: For inpatient profee palsy coding, the most critical rule is etiology-first sequencing for facial palsy — when a specific infectious or systemic cause is identified (VZV → B02.21, Lyme disease → A69.22), that etiology code is sequenced as principal and G51.0 is excluded; coding G51.0 alongside B02.21 is an ICD-10-CM Excludes1 violation and one of the most commonly flagged facial palsy coding errors in payer audits. Never code G51.0 as “facial palsy” without ruling out secondary causes — the ICD-10-CM includes “facial palsy” as an inclusion term under G51.0, meaning a coder who sees only “facial palsy” in the documentation must ensure no specific etiology (stroke, zoster, Lyme, tumor) is documented elsewhere in the chart before defaulting to G51.0; if the attending documents “facial palsy” without specifying Bell’s palsy, a physician query is warranted. Undercoding alert:G23.1 (progressive supranuclear palsy) is one of the most chronically undercoded neurodegenerative diagnoses on inpatient profee claims — it is a CC per CMS MS-DRG and frequently gets missed when attendings document “PSP” in shorthand without spelling out the full diagnosis; documentation trigger phrases include “vertical gaze palsy,”“Steele-Richardson-Olszewski,”“PSP,” and “axial rigidity with early falls” — any of these should prompt a physician query for the formal diagnosis. For birth-related palsy, the P14.x codes are neonatal-only (used during the birth encounter or neonatal admission) — if a child presents years later for Erb’s palsy sequelae, the correct code is G54.2 (cervical root disorder/brachial plexopathy) with documentation of the birth etiology noted in history; never use P14.0 on an adult or pediatric outpatient claim. Modifier -52 (reduced services) is appropriate when a planned bilateral EMG (95868) is only partially completed due to patient tolerance or limited exam findings.
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