Differential Diagnosis in Neurology

14.4. Dystonia

• General characteristic
  • Definition: Slow, sustained involuntary movements and postures that involve both axial and proximal muscles
  • Predominant characteristics:
    • Slow and axial-athetotic dystonia
    • Superimposed involuntary jerks-myoclonic dystonia
    • Dystonic postures:
      • Torticollis; tortipelvis
      • Scoliosis and lordosis
      • Dropped, inverted and plantar flexed foot
    • Dystonic tremor:
      • Fast distal tremulous movements
  • Excessive cocontraction of antagonist muscles during a voluntary movement
  • Spreading contraction of muscles not needed for a specific movement
  • Spontaneous cocontraction of agonists and antagonist muscles

• Distribution
  • Generalized
  • Segmental (two contiguous areas)
  • Focal (one extremity or motor group)
  • Multifocal (two or more body parts)

• Clinical Features
  • Generalized dystonia is most often seen in young patients
  • Focal and segmental dystonia occurs in middle age to older patients
  • Muscle groups most frequently involved are:
    • Orbicularis oculi
    • Forearm flexors
    • Wrist flexors
    • Inverters of the foot
    • Sternocleidomastoid
  • Specific movements are repetitive
  • Sensory tricks are common (early):
    • Finger to one eye to block blepharospasm
    • Finger to forehead to black torticollis
  • Action dystonia:
    • Early in the course of the disease only the muscles that are used are affected
    • Later dystonia spreads to other non-used groups
    • Aggravated by specific activities

Dystonia by Etiology

• Primary dystonia:
  • Idiopathic torsion dystonia:
    • Hereditary
    • Sporadic
  • Focal segmental, multifocal (including adult onset).
    • Cranial dystonia (oculo-oro-mandibular)
    • Spasmodic torticollis
    • Writer's cramp
    • Spasmodic dysphonic
    • Musicians
    • Overuse syndromes
  • Autosomal dominant alcohol responsive myoclonic dystonia
  • Benign idiopathic dystonia of children
  • Idiopathic paroxysmal dystonia:
    • Paroxysmal kinesogenic dystonia
    • Paroxysmal non-kinesogenic dystonia
    • Intermediate forms
• Secondary dystonias:
  • Metabolic defects
  • Presumed metabolic defects
  • Neuronal degenerations
  • Non-degenerative conditions
  • Psychogenic dystonia

Idiopathic Torsion Dystonia

• General characteristics:
  • Genetics:
    • AD; chromosome 9; ITD1 gene
    • Reduced penetrance in non-Jews
    • Single mutation
    • Sporadic cases
    • Incidence >1 in 15,000 persons
• Clinical features:
  • Begins as focal action dystonia
  • 15–70% chance to generalize
  • Usually plantar flexion and inversion of the foot while walking
  • 5–10 years to reach maximum disability
  • May stabilize and a few may improve; partial remissions occur
  • Different manifestations within the same family; some family members generalize while others remain focal

Focal, Segmental or Multifocal Dystonia

Spasmodic Torticollis

• General characteristics:
  • Usually sternocleidomastoid mastoid and trapezius muscles are most affected; scalene muscles are affected early
  • More frequent in women than men
  • Tonic or clonic contracture of neck musculature:
    • Fixed and spastic deviation of the head to an awkward position (retro, latero or enterocolic)
  • Named by the sternocleidomastoid muscle that contracts
  • Movements are jerky early in the course of the disease
  • Sensory tricks; touching the forehead, resting the back of the head on an object is effective in blocking the specific dystonia; effect lost with time
  • Pain and tension are noted in the absence of head turning
  • High incidence of postural tremor and essential tremor
  • Progresses for 5 years and then stabilizes; a minority regress
  • Remissions (partial or full) occur < 5 years of onset
  • Sustained remissions 12–23%
  • May start 4–5th decade; hereditary cases have been noted
  • Occasionally caused by compression of the XI nerve by major artery in the posterior triangle of the neck

Oromandibular Dystonia

• Clinical features:
  • Forced dystonic mouth opening
  • Tongue protrusion
  • Involuntary jaw clenching
  • Mutilation of lips and tongue due to teeth
  • Impaired swallowing due to dystonia of pharyngeal muscles

Differential Diagnosis of Torticollis

• Mechanical cervical spine defects:
  • Spondylosis
  • Rotary facet subluxation
  • Spondylolisthesis
• Syringomyelia (often secondary to astrocytoma or hemangioblastoma)
• Chronic regional pain syndrome:
  • Cervical plexus traction injury
• Posterior fossa tumor (dural irritation or direct irritation of C2–C3 roots)
• Lesions of the lenticular or caudate nucleus

Writer's Cramp (Action Dystonia)

• General characteristics:
  • 25% of index patients have relatives with dystonia
  • Possible AD hereditary with reduced penetrance
  • Appears second to fourth decade
• Clinical features:
  • Specific fingers (often 4th or 5th) are involved early
  • Occurs with prolonged writing early in its course, then onset is immediate in those who write a great deal

Spasmodic Dysphonia (SD)

• General characteristics:
  • Tremulous voice
  • Forced with low tone and volume
  • Associated with facial grimacing
  • Abnormality of striatal, pallidal, SMA and thalamic motor loop
• Clinical features:
  • Three types of spasmodic dysphonia:
  • Adductor SD:
    • Involuntary hyper adduction of the vocal folds (strangled voice quality)
  • Mix SD:
    • Characteristics of both
  • General features of all SD:
    • Hoarseness
    • Pitch breaks
    • Poor range of intensity
    • Poor intensity control

Associated Neurological Features

• Tremor
• Poor rapid alternating movements
• Voice tremor

Blepharospasm

• Bilateral
• Severely interferes with vision:
  • Some patients think they are blind
• Sensory tricks:
  • Dark glasses (usually helpful)
  • Singing, talking, neck extensions, reading, chewing may either increase or decrease its occurrence
  • Prying one eye open breaks bilateral blepharospasm
• Blepharospasm and oro-mandibular cranial dystonia (Meige's or Burgher's Syndrome):
  • Severe blepharospasm
  • Associated with both oral and facial musculature dystonia
• Overuse dystonias:
  • Musicians
  • Athletes
  • Clinical features:
    • Specific activities or positions initiate the dystonia
    • Usually after years of repetition of specific movements
    • Spreads
    • Permanent
• Alcohol responsive myoclonic dystonia:
  • AD
  • Responds to alcohol
  • Essential myoclonus
• Benign idiopathic dystonia:
  • Described in infants
  • Resolves by age 3
  • May start in arm or leg
• Paroxysmal kinesigenic choreoathetosis (dystonia):
  • AD; AR; sporadic forms
  • Males affected greater than females
  • Clinical features:
    • Provoked by sudden movement
    • Prolonged excessive startle response
    • May have up to one hundred attacks/day
    • Responds to phenytoin

Idiopathic Paroxysmal Non-Kinesigenic Choreoathetosis (Dystonia)

• General characteristics:
  • AD, chromosome
• Clinical features:
  • Attacks may last for minutes to hours
  • Three attacks per day is not unusual
  • Fatigue, stress, caffeine, alcohol may trigger attacks
  • Responds to clonazepam

Secondary Dystonias

• General features:
  • Isolated dystonic posture
  • No other neurologic deficits
  • Perinatal and early development is normal
  • No prior drug history
  • Sudden onset
  • Rapid progression
  • Unusual distribution
• Dystonias associated with specific disease entities:
  • Parkinson's disease
  • Huntington's disease
  • Hallervorden–Spatz disease (PANK2)
  • Progressive supranuclear palsy
  • Segawa's disease
  • Ceroid lipofuscinosis
  • Sea-blue histiocytosis
  • Leigh's disease
  • Wilson's disease
  • Lesch–Nyhan syndrome
  • GM1, and GM₂ gangliosidosis
  • Fahr's disease
  • Niemann Pick Type C
  • Metachromatic leukodystrophy
  • Glutamic acidemia Type I
  • Homocystinuria
• Acquired dystonia:
  • Chronic regional pain syndrome
  • Trauma to the neck (sensitization of the cervical plexus)
  • Striatal motor loop lesions

Congenital Dystonias

• Kernicterus
• Anoxia
• Intrauterine stroke:
  • Porencephalic cyst
  • Middle cerebral artery distribution; lenticulostriate stroke; M1 segment caudate/putamen involvement with dystonia
  • Delayed onset is characteristic
  • Associated with higher cortical function and pyramidal deficits
• Focal lesions (striatum and/or thalamus):
  • Arteriovenous malformations
  • Infarcts (delayed onset; occurs after resolution of hemiparesis)
  • Head trauma
  • Brain tumor
  • Peripheral trauma (CRPSI/II)
  • Birth injury
• Drugs:
  • Primarily D2 receptor agonists:
    • Acute: tardive dystonic
    • Tardive: tardive dystonia
  • Levodopa