Neurological Occupational Diseases

Assoc. Prof. Pavel Urban, M.D. Ph.D.

Proportion of Neurological Occupational Diseases in the Total Number of Occupational Diseases

0

5

10

15

20

25

30

35

1996 1997 1998 1999 2000 2001 2002 2003 2004

Year

Peerc

en

t

Main Categories of Occupational Diseasesin 2004

28%28%28%28%

21%21%21%21%21%21%21%21%

17%17%17%17%

2%2%2%2%

11%11%11%11%

NeurologicalNeurologicalNeurologicalNeurological

Respir ator yRespir ator yRespir ator yRespir ator y

DermatosesDermatosesDermatosesDermatoses

InfectionsInfectionsInfectionsInfections

IntoxicationsIntoxicationsIntoxicationsIntoxications

Other sOther sOther sOther s

Neurological Occupational Diseases in 2004

84%84%84%84%

10%10%10%10%

1%1%1%1% 4%4%4%4% 1%1%1%1%

Carpal tunnel syCarpal tunnel syCarpal tunnel syCarpal tunnel sy

Cubital tunnel syCubital tunnel syCubital tunnel syCubital tunnel sy

CombinationsCombinationsCombinationsCombinations

Neur oboreliosisNeur oboreliosisNeur oboreliosisNeur oboreliosis

Tick-borne encephalitisTick-borne encephalitisTick-borne encephalitisTick-borne encephalitis

Prerequisites for a Diagnosis of a Neurological Occupational Disease

• Typical clinical manifestation

• Reasonable exclusion of alternativecauses

• Proof of relevant exposure

• Appropriate temporal association between exposure and disease

Neurological Occupational Diseases Caused by Chemical Noxae

(1) Toxic Encephalopathy

Clinical Manifestationof Toxic Encephalopathy

• Pseudoneurasthenic syndrome

• Psychoorganic syndrome

• Dementia

Laboratory Testsfor Toxic Encephalopathy

• Psychological examination

• Electroencephalography

• Evoked potentials (P300, VEP, BAEP)

• Neuroimaging methods (CT, NMR, PET, SPECT)

The Most Frequent Causes of Occupational Toxic Encephalopathy

Parkinsonian syndromeManganese

Parkinsonian syndromeCarbon monoxide

ErethismMercury vapor

Euphoria,

pseudohallucinations

Toluene

Psychiatric disordersCarbon disulphide

Solvent syndromeOrganic solvents mixture

Differential Diagnosisof Toxic Encephalopathy

• Non-toxic causes of diffuse encephalopathy

– Aging

– Incipient neurodegenerative disorder

• Non-occupational neurotoxicants

– Alcohol

– Drug abuse

Treatment of Toxic Encephalopathy

• Removal from exposure

• Nootropic drugs

– Piracetam

– Gingko biloba preparations

• Free radicals scavengers

– Vitamin E

(2) Toxic Neuropathy

General Characteristicsof Toxic Neuropathy

• Symmetrical

• Sensorimotor

• Distal

• Polyneuropathy

• Distal axonopathy – “dying back process“

Clinical Manifestationof Toxic Polyneuropathy

• Sensory disturbances

– Paresthesiae and numbness in a “gloves and stockings” distribution

– Tactivle, thermal, and vibratory sensation diminished

• Deep tendon reflexes diminished or absent

• Motor disturbances

– Usually mild

– Initial sign: dorsiflexion of the big toe weakened

Laboratory Testsfor Toxic Polyneuropathies

• Nerve conduction studies (the sural and tibial nerves)

• Electromyography

• Quantitative sensory testing

• Somatosensory evoked potentials (detection of toxic myelopathy)

• Central-peripheral distal axonopathy

Most Frequent Causes of Occupational Toxic Neuropathies

Acrylamide, TCDD, Organophosphates

Others

Carbon disulphide, Trichlorethylene, n-Hexane

Organic solvents

Lead, Thalium, Mercury

Toxic metals

Differential Diagnosisof Toxic Neuropathy

• Alcoholic polyneuropathy

– CDT – Carbohydrate Deficient Transferin

• Diabetic polyneuropathy

• Paraneoplastic polyneuropathy

Treatment of Toxic Polyneuropathy

• Removal from exposure

• Vasoactive drugs

• Vitamins (B1, B6, B12, E)

• Antiepileptic drugs

– carbamazepin

– gabapentin

– pregabalin

Neurological Occupational Diseases Caused by Physical Factors

(1) Long-term overload of extremities by physical work

(2) Working with vibrating tools

(1) Long-term overload of extremities by physical work

(1) Heavy physical work

(2) Highly repetitive movements

Occupation-Related Compressive Neuropathies

• Upper extremities

– Median nerve

• Pronator teres syndrome

• Carpal tunnel syndrome

– Ulnar nerve

• Cubital tunnel syndrome

• Canalis Guyoni syndrome

– Radial nerve

• Supinator syndrome

• Lower extremities

– Fibular nerve

– Tibial nerve

• Tarsal tunnel syndrome

Carpal Tunnel Syndrome

Etiology of Carpal Tunel Syndrome

• Endogenous factors

– Inflammation• Tendinitis

• Dermatomyositis

– Endocrinological changes• Pregnancy

• Birth control pills

• Ovarial hypofunction

• Hypothyroidism

– Metabolic changes• Diabetes mellitus

• Gout

• Exogenous factors

– Post-traumatic changes

– Manual work

ahok

Types of Occupational ActivitiesRelated to CTS

• Static overload due to forceful and repetitive contraction of flexor muscles in the forearm

– Examples: working with a hammer or grinder, manipulating heavy loads

• Stereotyped repetitive flexion-extension of fingers

– Examples: manual cow-milking, typing, playing musical instruments

• Activities involving pinching, screwing etc.

– Examples: clockmakers, minute work

• Direct pressure on the wrist

– Examples: dentists, bikers, working with scissors

Subjective Symptoms of CTS

• Numbness upon awaking

• Nocturnal paresthesiae (“Brachialgiaparesthetica nocturna”)

• Daily paresthesiae

• Clumsy hand movements

Objective Signs of CTS

• Hypesthesia in the distal median area

• Weakness of the abductor pollicis brevis muscle

• Muscle and skin trophic changes

• Local findings

– Punctum dolorosum

– Pseudoneuroma

• Provocative tests

– Tinel’s sign

– Phalen’s sign (Flexion test)

– Extension test

– Elevation test

– Digital compression test

Laboratory Diagnostic Tests for CTS

• X-ray examination

• CT, NMR

• Quantitative sensory testing

• Nerve conduction studies

• Needle electromyography

Differential Diagnosis of CTS

• Proximal median neuropathy (pronator teressyndrome)

• Brachial plexopathy (upper trunk)

• Thoracic outlet syndrome

• Cervical radiculopathy (especially C6)

• Polyneuropathy

Treatment of CTS

• Removal from exposure

• Splinting of the wrist

• Vasoactive drugs

• Nonsteroidal anti-inflammatory drugs

• Local application of corticosteroids

• Surgery

Occupational Compressive Neuropathiesin the Lower Extremities

• Compression of the Fibular nerve

– Examples: potato-lifters, miners, pavers, carpetlayers

• Tarsal tunnel syndrome (Tibial nerve)

– Examples: ballet dancers, jockeys, long-distance runners

PNS Damage Caused by Working with Vibrating Tools

• Mononeural lesion

– Pathophysiological mechanism: compressiveneuropathy

– Most frequently - CTS

• Bineural lesion

– Pathophysiological mechanism: ischemicneuropathy

– Both the median and ulnar nerves damaged

– Frequent association with vibration white fingers

Occupational Cramps

• Synonyms– Occupational spasms– Occupational neuroses

• Examples– Graphospasm – Telegraphist’s cramp – Trumpeter’s mouth– Horn player’s torticollis

• Pathopysiology– Focal dystonia?– Psychogenic origin?

• Treatment– Behavioral techniques– Botulinum toxin injections