SECTION 3 Neurology

Neuroanatomy illustrations

Figure 3.1 Lateral view of right cerebral hemisphere.

Figure 3.2 Medial view of right cerebral hemisphere.

Figure 3.3 Mid-sagittal section of the brain.

Figure 3.4 Horizontal section through the brain.

Figure 3.5 Coronal section of the brain.

Figure 3.6 Lateral view of sensory and motor cortical areas.

Figure 3.7 Medial view of sensory and motor cortical areas.

Figure 3.8 Lateral view of right hemisphere showing territories supplied by the cerebral arteries.

Figure 3.9 Ascending and descending spinal cord tracts.

Ascending tracts	Descending tracts
Gracile fasciculus – proprioception and discriminative touch in legs and lower trunk	Lateral corticospinal – voluntary movements
	Medullary retrospinal – locomotion and posture
Cuneate fasciculus – proprioception and discriminative touch in arms and upper trunk	Pontine reticulospinal – locomotion and posture
Posterior and anterior spinocerebellar – reflex and proprioception	Vestibulospinal – balance and antigravity muscles
Lateral spinothalamic – pain and temperature	Tectospinal – orientates head to visual stimulation
Anterior spinothalamic – light touch	Anterior corticospinal – voluntary movements

Signs and symptoms of cerebrovascular lesions

Figure 3.10 Middle cerebral artery.

Signs and symptoms	Structures involved
Contralateral weakness/paralysis of face, arm, trunk and leg	Motor cortex (precentral gyrus)
Contralateral sensory impairment/loss of face, arm, trunk and leg	Somatosensory cortex (postcentral gyrus)
Broca’s dysphasia	Motor speech area of Broca (dominant frontal lobe)
Wernicke’s dysphasia	Sensory speech area of Wernicke (dominant parietal/temporal lobe)

Signs and symptoms	Structures involved
Neglect of contralateral side, dressing and constructional apraxia, geographical agnosia, anosognosia	Parietal lobe (non-dominant lobe)
Homonymous hemianopia (often upper homonymous quadrantanopia)	Optic radiation – temporal fibres
Ocular deviation	Frontal lobe
Gait disturbance	Frontal lobe (usually bilateral)
Pure motor hemiplegia	Posterior limb of internal capsule and adjacent corona radiata
Pure sensory syndrome	Ventral posterior nucleus of thalamus

Figure 3.11 Anterior cerebral artery.

Signs and symptoms	Structures involved
Contralateral hemiplegia/hemiparesis (lower limb > upper limb)	Motor cortex
Contralateral sensory loss/impairment (lower limb > upper limb)	Somatosensory cortex
Urinary incontinence	Superior frontal gyrus (bilateral)
Contralateral grasp reflex	Frontal lobe
Akinetic mutism, whispering, apathy	Frontal lobe (bilateral)
Apraxia of left limbs	Corpus callosum
Tactile agnosia	Corpus callosum
Spastic paresis of lower limb	Bilateral motor leg area

Figure 3.12 Posterior cerebral artery.

Signs and symptoms	Structures involved
Thalamic syndrome: hemisensory loss, chorea or hemiballism, spontaneous pain and dysaesthesias	Posterior nucleus of thalamus
Weber’s syndrome: oculomotor paralysis and contralateral hemiplegia	Cranial nerve III and cerebral peduncle
Contralateral hemiballism	Subthalamic nucleus
Contralateral homonymous hemianopia	Primary visual cortex or optic radiation
Bilateral homonymous hemianopia, visual hallucinations	Bilateral occipital lobe
Alexia, colour anomia, impaired memory	Dominant corpus callosum (occipital lobe)
Memory defect, amnesia	Bilateral inferomedial portions of temporal lobe
Prosopagnosia	Calcarine sulcus and lingual gyrus (non-dominant occipital lobe)

Signs and symptoms	Structures involved
Lateral medullary syndrome: – vertigo, vomiting, nystagmus – ipsilateral limb ataxia – ipsilateral loss of facial pain and thermal sensation – ipsilateral Horner’s syndrome – ipsilateral dysphagia, hoarseness, vocal cord paralysis and reduced gag reflex – contralateral loss of pain and thermal sensation in trunk and limbs	Vestibular nuclei Spinocerebellar tract Cranial nerve V Descending sympathetic tract Cranial nerves IX and X Lateral spinothalamic tract
Ipsilateral tongue paralysis and hemiatrophy	Cranial nerve XII
Contralateral impaired tactile sensation and proprioception	Medial lemniscus
Diplopia, lateral and vertical gaze palsies, pupillary abnormalities	Cranial nerve VI, medial longitudinal fasciculus
Bulbar palsy, tetraplegia, changes in consciousness	Bilateral corticospinal tracts
Pseudobulbar palsy, emotional instability	Bilateral supranuclear fibres, cranial nerves IX–XII
Locked-in syndrome	Bilateral medulla or pons
Coma, death	Brainstem

Function	Signs of impairment
Precentral gyrus (motor cortex)	Contralateral hemiparesis/hemiplegia
Contralateral movement: face, arm, leg, trunk
Broca/s area (dominant hemisphere)	Broca/s dysphasia (dominant)
Expressive centre for speech
Supplementary motor area Contralateral head and eye turning	Paralysis of contralateral head and eye movement
Prefrontal areas ‘Personality’, initiative	Disinhibition, poor judgement, akinesia, indifference, emotional lability, gait disturbance, incontinence, primitive reflexes, e.g. grasp
Paracentral lobule	Incontinence of urine and faeces
Cortical inhibition of bladder and bowel voiding	Incontinence of urine and faeces

Function	Signs of impairment
Postcentral gyrus (sensory cortex) Posture, touch and passive movement	Hemisensory loss/disturbance: postural, passive movement, localization of light touch, two-point discrimination, astereognosis, sensory inattention
Supramarginal and angular gyri
Dominant hemisphere (part of Wernicke’s language area): integration of auditory and visual aspects of comprehension	Wernicke’s dysphasia
Non-dominant hemisphere: body image, awareness of external environment, ability to construct shapes, etc.	Left-sided inattention, denies hemiparesis
	Anosognosia, dressing apraxia, geographical agnosia, constructional apraxia
Dominant parietal lobe Calculation, using numbers	Finger agnosia, acalculia, agraphia, confusion between right and left
Optic radiation Visual pathways	Homonymous quadrantanopia

Function	Signs of impairment
Superior temporal gyrus (auditory cortex) Hearing of language (dominant hemisphere), hearing of sounds, rhythm and music (non-dominant)	Cortical deafness, difficulty hearing speech – associated with Wernicke’s dysphasia (dominant), amusia (non-dominant), auditory hallucinations
Middle and inferior temporal gyri Learning and memory	Disturbance of memory and learning
Limbic lobe Smell, emotional/affective behaviour	Olfactory hallucination, aggressive or antisocial behaviour, inability to establish new memories
Optic radiation Visual pathways	Upper homonymous quadrantanopia