ATAXIA

Gross incoordination of muscle function leading to staggering and irregular muscle movements.

Manifestation of:

a- spinal cord diseas

b - cerebellar dysfunction

c-vestibular dysfunction 

Ataxia - 

Spinal Cord Origin

Ataxia plus: 

*Weakness

*Postural Reaction Deficit

* Cranial Nerve function typically normal

Ataxia -

Vestibular Origin: 

Ataxia plus:

* Head tilt

*Nystagmus

Ataxia -

Cerebellar origin:

Ataxia plus:

* No weakness

*Ataxia of all 4 limbs plus head/neck

Paresis - definition: 

Partial loss or impairment of movement resulting in weakness of muscle action.

Paralysis - definition:

Complete loss of function of one or more muscle groups. 

Hemiparesis:

Paraparesis: 

Tetraparesis:

H - Unilateral paresis of both fore and hindlimb

P -  Paresis of both fore or both hind limbs

T - Paresis of all four limbs 

Paresis -

Cerebral Cortex origin

Unilateral lesion: 

*Contralateral hemiparesis of limbs

*Mild, often undetectable 

*Contralateral postural reaction deficits 

Paresis -

Brain stem origin

Unilateral lesion:

 *Ispilateral hemiparesis

*Severe

*Ipsilateral postural reaction deficits 

*Usually accompanied by cranial nerve signs 

Upper Motor Neuron Signs: 

 *Spasticity

* Brisk reflexes

*No fasciculations 

*Possible sensory disturbances 

Lower Motor Neuron Signs: 

 *Weakness and Muscle Atrophy and Fasciculations

*Depressed spinal reflexes 

*Possible sensory disturbances (maybe without reflex loss - noted by ataxia or self mutilation)

* Often begins in hindlimbs and progresses to all 4 

Spinal Cord Lesions -

C1-C5 

* Mild - tetraparesis

   +Ataxia  (Rear>Fore)

* Severe - + postural reaction deficits 

Spinal Cord Lesions -

C6 - T2

(brachial intumescence) 

 * Tetraparesis  + Ataxia

* Conscious proprioception possibly lost in all

4 limbs if severe

* Fore >Hindlimb effected 

Spinal Cord Lesions -

T3 - L3 

* Hindlimb paresis + UMNSx

* Postural reaction deficit

*Conscious Proprioception deficit

*Forelimbs normal 

Lower Motor Neuron Signs -

Diseases that affect: 

* Peripheral nerves

* Neuromuscular junction

* Nerve cell bodies in  ventral grey matter of the cervical and lumbosacral intumescences.

Upper Motor Neuron Signs -

Diseases or damage affecting: 

* Cells of ventral horn of spinal cord

(except at cervical and lumbosacral intumescences) 

Motor Neuron Diagram

Diseases resulting in diffuse LMN Damage:

* Disorders of demyelination or axonal degeneration (congenital or familial)

*Inflammatory immune mediated nerve disorders

*Polyneuropathy - metabolic, toxic or neoplastic 

*Neuromuscular junction toxicity (botulism/tick paralysis) 

Clinical Grading of Rearlimb Paresis and Ataxia

Grade 0

* No purposeful movement

*Paraplegia

Clinical Grading of rearlimb paresis and ataxia

Grade 1 

*Unable to weight bear

* Slight limb movement when supported

* Severe Paraparesis

Clinical grading of rearlimb paresis and ataxia

Grade 2 

* Unable to weight bear

* Readily moves limbs when supported but stumbles and falls

* Moderate paraparesis and ataxia 

Clinical grading of rearlimb paresis and ataxia

Grade 3 

* Can weight bear but frequently stumbles and falls

* Drunken sailor gait

* Mild paraparesis and ataxia 

Clinical grading of rearlimb paresis and ataxia

Grade 4 

* Weight bearing fine

* Minimal paraparesis and ataxia

Clinical grading of rearlimb paresis and ataxia

Grade 5

* Normal strength

* No apparent paresis or ataxia

Episodic Weakness

Disorders causing: 

* Disorders of skeletal muscle (polymyostitis, myopathies)

 *Myasthenia gravis

*Cardiopulmonary disease

* Rupture of vascular neoplasms

* Several metabolic disorders that secondarily affect the CNS (hypoglycaemia, hypoadrenocortism)

Dysmetria and Hypermetria -

Definition: 

Dysmetria - Inability to accurately control the range of movement of muscular acts

Hypermetria - ataxia in which over-reaching of intended goal of movement occurs 

Damage to Cerebellum or Spinocerebellar Tracts

*Strong but Uncoordinated 

* Ataxia

 * Intention Tremor +/- fine tremor at rest

 *Hypermetria and Dysmetria 

 *No paresis 

* +/- menace reflex 

Cerebellar Damage Etiology

Static or improve with time:

* Haemorrhage

* Trauma

* Infarction

 Invariably Progressive:

*Infectious inflammatory disease

*Granulomatous meningocephalitis

*Primary or metastatic neoplasm 

3 Types of

Inherited and congenital cerebellar syndromes

*Cerebellar Hypoplasia -

early onset, non-progressive (eg from perinatal parvo infection)

*Neonatal Cerebellar Neuronal Abiotrophy -

early onset, progressive

*Postnatal Cerebellar Neuronal Abiotrophy -  

late onset, progressive

Diagnosis of Cerebellar dysfunction variants:

* Cerebellar signs w/o other symptoms

*Congenital hypoplasia

*Malformations

*Abiotrophy 

Diagnosis of Cerebellar dysfunction variants:

*Inflammatory or Neoplastic diseases 

* Cerebellar signs +

* Other neurologic abnormalities evident and identifiable on testing (radiographs, clinicopathological tests, CSF analysis etc)

 Diagnosis of Cerebellar dysfunction variants:

* Degenerative diseases 

* Cerebellar signs +

* Other neurological abnormalities

*No evidence of neoplasm/infection on testing

*Diagnosis on biopsy or post-mortem 

4 Types of

Involuntary alterations in muscle tone 

*Tremors

* Tetany

*Tetanus

*Opisthotonus 

Tremors 

 *Characterised by involuntary quivering or

trembling of the muscle. 

*Acute onset - suspect toxicity - metaldehydes, organophosphates, chlorinated hydrocarbons

 * Metabolic disorders - hypoglycaemia, hypocalcaemia 

 *"Shaker" dogs - relieved with sleep, increased

with excitement. No⁺ves on testing.

* Congenital diffuse tremor -abnormal myelination in puppies. Increase with exercise, and excitement. Evident with start of ambulation.

Grows out of it.

Tetany 

* More severe and generalised muscle trembling

*Similar diagnostics to tremors

*May progress to seizures 

Tetanus

* Sustained tonic contraction of muscles, no twitching

*Seen with loss of consciousness with severe brainstem damage due to neoplasia, infection or trauma. 

*Commonly with no change in consciousness with mild strychnine poisoning, trauma to rostral cerebellum and infection by clostridium tetani

Opisthotonos 

* Very severe tetanus

*Spasm of limb and neck muscles - can --> respiratory failure

*Resultant lateral recumbency

*Dorsoflexion of neck  and Extensor rigidity of limbs