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Neurological exam - Coggle Diagram

- - - - hyposmia
      - anosmia
      - e.g. may present as decreased appetite
        
        non-neuro causes e.g. rhinitis = more common
  - - - Rods and cones (neuroepithelial cells of retina)
        
        ganglion cell of the retina. Its axon lies in the optic nerve and continues through the optic chiasm and proximal part of the optic tract on the opposite side (66% cats, 75% dogs decussation)
        
        cell body of the 3rd neuron is located in the lateral geniculate nucleus in the diencephalon. Its axon projects to the visual cortex in optic radiations
  - - - afferent CN = CNV trigeminal (ophthalmic or maxillary)
      - Intermediate brain region = brainstem
      - efferent CN = CNVII facial
      - blink elicited by touching the medial or lateral canthus of the eye
    - - Afferent CN = CNV trigeminal (opthalmic)
      - Intermediate brain region = brainstem
      - efferent CN=CNVII facial + CNVI abducent
      - blink and globe retraction elicited by touching the cornea
    - - efferent CN=CNVIII vestibulocochlear
      - Intermediate brain region = brainstem
      - efferent CN = CNIII oculomotor, CN IV trochlear, CNVI abducent
      - nystagmus induced by moving the head
    - - afferent CN= optic
      - intermediate brain region = forebrain, cerebellum, brainstem
      - efferent CN=CNVII facial
      - blink elicited by menacing gesture
      - present from about 10-12 weeks in dogs and cats
    - - afferent CN = trigeminal (opthalmic)
      - intermediate brain region = forebrain, brainstem
      - no efferent CN
      - withdrawal of head elicited by touching the nasal mucosa
    - - afferent CN - optic
      - Intermediate brain region = brainstem
      - efferent CN - oculomotor
      - pupillary restriction elicited by shining a light in the eye
    - - afferent CN - CN IX glossopharyngeal, CNX vagus
      - Intermediate brain region = brainstem
      - efferent CN - CN IX glossopharyngeal, CNX vagus
      - contraction of the pharynx elicited by its palpation
  - - - ventrolateral strabismus
        
        differentiate from vestibular strabismus, which only occurs in certain head positions (positional strabismus)
      - inability to rotate the eye dorsally, ventrally or medially during oculovestibular testing
        
        external ophthalmoplegia
      - these signs can also be associated with a dilated unresponsive pupil (internal ophthalmoplegia) +/- narrowing of the palpebral issue (ptosis of the upper eyelid)
  - - - responsible for inward rotation of the eyeball
    - - best evaluated by fundoycopic examination, observing temporal deviation of the dorsal retinal vessels.
      - rare finding, lesions of this nerve usually occur in combination with lesions of CNIII + CN VI, producing internal and external ophthalmoplegia
  - - - mucosa of nasal septum
      - mucosa of oral cavity
      - cornea
      - cutaneous regions of face
    - - temporalis
      - masseter
      - medial and lateral pterygoid
      - rostral part of the digastric muscles
    - - ophthalmic
        
        cornea
        
        medial canthus of eye
        
        nasal spatial mucosa
        
        skin on dorsum of nose
      - maxillary
        
        lateral canthus
        
        skin of cheek
        
        side of nose
        
        muzzle
        
        palates
        
        mucous membrane of the nasopharynx
        
        teeth
        
        gingiva of upper jaw
      - mandibular
        
        mandibular portion of face and oral cavity
    - - unilateral involvement of motor part of CNV causes ipsilateral masticatory muscle atrophy and decreased jaw tone
        
        enophthalmia and protrusion of 3rd eyelid can be observed in ipsilateral eye
        
        passive retraction of eyeball due to loss of the temporalis muscle mass
      - bilateral involvement of the motor branches results in dropped jaw and inability to close mouth voluntarily
      - decreased/complete loss of facial sensation is defined as facial hypoaesthesia or anaesthesia
      - involvement of the ophthalmic branch of CNV --> decreased tear secretion and neurotropic keratitis 2ry to loss of afferent stimulation to the lacrimal reflex
  - - - ipsilateral convergent strabismus
      - inability of eye to cross the midline when evaluating the horizontal physiological nystagmus
      - inability to retract the eyeball
      - isolated lesions rare
  - - - motor
        
        drooping of and inability to move ear and lip
        
        widened palpebral fissue
        
        absent spontaneous and provoked blinking
        
        deviation of nose toward normal side due to unopposed muscle tone on the affected side
        
        with chronic denervation, lips are retracted further than normal and the nostril is deviated to the affected side as a result of muscle fibrosis
        
        facial spasm
      - unilateral
        
        asymmetry of ears, eyelids, lips and nose
        
        lesions of individual branches leads to paresis and paralysis of the specific muscles they innervate
        
        dysfunction of the parasympathetic supply of the lacrimal gland -> keratoconjunctivitis sick KCS
  - - - head tilt
      - rolling
      - falling
      - leaning
      - circling
      - abnormal +/- positional nystagmus
      - positional strabismus
      - asymmetrical ataxia
  - - - Sensory
        
        caudal 3rd of tongue
        
        pharyngeal mucosa
      - musculature of the pharynx and palatine structures
      - parasympathetic innervates the parotid and zygomatic salivary glands
      - dysfunction
        
        dysphagia
        
        absent gag reflex
        
        reduced pharyngeal tone
        
        animals frequently cough after drinking and swallow repeatedly due to accumulation of saliva in the pharynx
    - - controls motor function of larynx (recurrent laryngeal branch), pharynx and oesophagus
      - sensory to the larynx, pharynx and thoracic and abdominal viscera
      - parasympathetic
        
        innervation to all thoracic and abdominal viscera, except those of the pelvic region
      - dysfunction
        
        dysphagia
        
        inspiratory dyspnoea(due to laryngeal paralysis)
        
        voice changes (dysphonia)
        
        regurgitation
        
        due to megaoesophagus in the case of bilateral vagal disorder
        
        pharyngeal and oculocardiac reflexes are absent
  - - - atrophy of trapezius muscle
      - neck may be deviated toward the affected side in chronic cases
  - - - problems with prehension, mastication and deglutition
      - if unilateral - tongue deviates toward contralateral side or if chronic protrudes toward the side of the lesion and atrophy is observed ipsilaterally
      - muscle fasciculation's may be obvious on the affected side of the denervated tongue
- - - - progressive
      - static
      - improving
      - waxing and waning
- - - - ascending reticular activating system (ARAS) within the brainstem
        
        receives input from all sensory modalities at both the level of the spinal cord and brainstem
        
        except muscle and joint proprioception
        
        ARAS then projects stimulatory input diffusely to all areas of the cerebral cortex via the thalamus to maintain consciousness
      - Cerebral cortex
    - - confused and disorientated
        
        responding to environmental stimuli in an inappropriate manner
      - Normal
        
        alert, normal response to environmental stimuli
      - Obtunded
        
        drowsiness, inattention and less responsive to environmental stimuli
      - Stuporous
        
        State of unconsciousness with reduced responses to external stimuli, but can be roused by painful stimulus
      - Comatose
        
        State of unconsciousness with absence of response to any environmental stimuli, including pain
    - - Delirium
      - disorientation
      - aggression
      - compulsive walking
      - loss of learned behaviour e.g. loss of toilet training
      - vocalising
      - Head pressing
      - Hemi-neglect syndrome
        
        with structural forebrain disease, animals ignore sensory input from one half of their environment
        
        lesion is on the contralateral side to 'ignored' side
  - - - often indicates a vestibular disorder (peripheral or central)
      - usually towards same side of lesion
      - lesions affecting the cerebellar portion of the vestibular apparatus (cerebellar peduncle or flocculonodular lobe)
        
        can cause a central vestibular syndrome with a paradoxical head tilt (head tilt contralateral to side of lesion)
    - - often associated with pleurothotonus (body turn) and circling
      - Aversion syndrome - often toward side of a forebrain lesion
    - - neuromuscular disorder or severe cervical spinal cord grey matter lesion or weakness e.g. systemic
      - more common in cats due to absence of nuchal ligament
    - - congenital/acquired/permanent/intermittent
      - common lesions
        
        malformed vertebrae e.g. hemivertebrae
        
        intraparenchymal spinal cord disease e.g. syringohydromyelia causing denervation of associated paraspinal musculature, producing asymmetrical muscle tension and subsequent vertebral deviation
        
        spinal pain e.g. disc herniation
      - Scoliosis
        
        lateral deviation of the spine
      - Kyphosis
        
        Dorsal curvature of the spine
      - Lordosis
        
        ventral curvature of the spine
      - Torticollis (twisting of the neck)
    - - observed as a realist of a rostral brainstem lesion (between the colliculi of the midbrain)
      - characterised by extension of limbs and opisthotonus
      - associated with a stuporous or comatose mental status
    - - spasm of the muscles causing backward arching/extension of the head, neck, and spine
    - - Rostral part of cerebellum inhibits the stretch reflex mechanism of antigravity muscles (extensor muscle tone)
      - opisthotonus with thoracic limbs extended
      - hips may be flexed by the increased tone in the iliopsoas muscles
      - mentation normal
      - Often caused by an acute cerebellar lesions and can sometimes be episodic
    - - Observed with acute severe thoracic or cranial lumbar spinal cord lesion in dogs
      - lesion may interfere with inhibitory ascending neurons (also known as border cells) that project cranially from the lateral grey matter of the cranial lumbar spinal cord segments to inhibit the thoracic limb extensor motor neurons
      - Extensor hypertonia of the thoracic limbs, with retention of voluntary movements and normal proprioceptive placing in these limbs, in addition to paralysis of the pelvic limbs
      - Pelvic limb paralysis is caused by direct interference with UMN system, but reflexes are intact in these limbs
        
        this decrease in tone is transient, only present in acute lesions and does not have any prognostic significance
    - - characteristic of a balance disorder with diseases particularly affecting the cerebellum
  - - - requires interaction between the UMN + LMN system
      - UMN system
        
        any efferent neuron originating within the brain and synapsing with an interneuron with a LMN to modify its activity
        
        Responsible for initiation and maintenance of normal movements and for the maintenance of tone in the extensor muscles to support body v gravity
        
        inhibitory effect on myotatic reflexes
        
        lesions typically result in loss of motor function and release of the inhibitory effect
      - LMN system
        
        connects the CNS with muscles of an effector organ
        
        Produce muscular contraction necessary to maintain posture, support bodyweight and provide gait.
    - - Uncoordinated gait
      - can arise from
        
        General proprioceptive ataxia
        
        lack of info reaching the CNS, which is responsible for awareness of movement and position of neck, trunk and limbs in space
        
        Abnormal postural reactions with limb paresis
        
        Vestibular ataxia
        
        head tilt, leaning, rolling to one side, abnormal nystagmus, strabismus, normal (peripheral), abnormal (central) postural reactions, crouched posture, reluctance to move and wide head excursion in case of bilateral dysfunction
        
        cerebellar ataxia
        
        wide based stance, intention tremors of head, loss of balance and truncal sway, dysmetric gait, pendular nystagmus, delayed onset and dysmetric hopping reactions, ipsilateral menace deficit with normal vision, absence of limb paresis and proprioception placement deficits, and normal mentation (pure cerebellar disease)
      - Further classification
        
        Hypometria
        
        shorter protraction phase of gait
        
        Hypermetria
        
        longer protraction phase of gait
        
        Dysmetria
        
        ability to control the distance, power and speed on an action is impaired (may be combination of hypometria and hypermetria)
    - - Loss of ability to support weight (LMN disorder) or an inability to generate gait (UMN disorder)
      - some voluntary movement still present
      - UMN Paresis
        
        delay in the onset of protraction (swing phase of gait)
        
        resultant stride longer than normal with a stiff quality of movement
        
        release of inhibitory effect UMN has on LMN
        
        spastic paralysis/paresis
      - LMN Paresis
        
        difficulty in weight bearing: varies from a short, choppy gait to a complete inability to support weight e.g. limb collapses whenever weight is placed on it.
        
        Compared with UMN paresis, disorders of the LMN system only cause paresis and not ataxia.
    - - more severe paresis with complete loss of voluntary movement
    - - Tetraparesis/tetraplegia
        
        paresis/paralysis of all 4 limbs, resulting from a lesion cranial to T3 or from a generalised LMN disorder
      - Paraparesis/paraplegia
        
        paresis/paralysis of the pelvic limbs caused by a lesion caudal to T2
      - Monoparesis/monoplegia
        
        paresis/paralysis of one limb, usually caused by a lesion of the lMN innervating the affecting limb
        
        very lateralised lesions caudal to T2 can also result in this
      - Hemiparesis/hemiplegia
        
        paresis/paralysis of the limbs on one side due to lesion cranial to T2
        
        This is ipsilateral to a lesion located between T2 and the caudal midbrain, and contralateral to a lesion located in the rostral midbrain or cerebrum
    - - Lesions in the vestibular system or by an asymmetrical/focal lesion in the forebrain
      - tight circles usually vestibular disorder
        
        usually associated with other signs of vestibular disorder (head tilt, nystagmus, strabismus or falling)
        
        usually ipsilateral to lesion
        
        exceptions: lesions affecting caudal cerebellar peduncle, fastigial nucleus and flocculonodular lobes of cerebellum
      - wide circles usually forebrain disorder
        
        usually toward the side of an asymmetrical/focal forebrain lesion
    - - short stride of affected limb and long stride of contralateral limb
      - orthopaedic pain
      - can be associated with nervous system dysfunction 'nerve root signature'
        
        referred pain down a limb, causing lameness or elevation of the limb
        
        as a result of entrapment of the spinal nerve, usually by a lateralised disc extrusion or nerve root tumour
  - - - clinical manifestation of excessive or hyper synchronous electrical activity in the cerebral cortex
      - focal or generalised
      - implies a forebrain disorder
      - intra or extra cranial
    - - sudden contraction followed by immediate relaxation of a specific muscle group
      - Sporadic
        
        benign + idiopathic
        
        form of a simple partial seizure due to a forebrain disorder
      - Repetitive
        
        constant
        
        often as a result of encephalitis or myelitis caused by canine distemper virus
        
        Action related
        
        congenital (often caused by a diffuse abnormality of CNS myelination)
        
        acquired
        
        e.g. idiopathic generalised tremor syndrome
        
        Postural
        
        head bobbing
        
        with rapid and repeated cycles, manifests as a tremor
    - - Synchronous involuntary oscillating contractions of antagonistic muscle groups
      - resting tremors (only present at rest)
      - intention tremors (when animal intends to move)
      - action tremors (postural or kinetic)
        
        occur following initiation of voluntary movement and worsen with increasing levels of activity
        
        disappear when animal is at rest
    - - sustained irregular contraction with delayed relaxation of a muscle or a group of muscles following voluntary contraction
      - occurs in certain congenital and acquired muscle disorders and is often asynchronous and asymmetrical
    - - undulating vermiform movement of the overlying skin due to contraction of small bands of muscle fibres
    - - paroxysmal onset of flaccid paralysis (muscle atone) with preservation of consciousness
      - lasts few seconds to a few minutes
      - attacks frequently induced by excitement and can be reversed by an external stimulus
      - can be accompanied by narcolepsy
    - - episodic sudden involuntary contractions of a group of skeletal muscles in a conscious patient with normal sensorium during rest or activity
      - dyskinesia
      - dystonia
      - chorea
      - athetosis
      - ballism
    - - common in bulldogs and dobermans
      - idiopathic
      - consequence of structural brain disease, esp with pathology affecting the thalamus