occipital lobes

Seminar 11-11-2009Lakshya J. Basumatary, M.D. DM (Neurology)

Trainee

Occipital Lobes

Association areas

Redrawn from Geschwind N: Specializations of the human brain. Sci Am 241:180, 1979.

Blood supply

• Posterior cerebral arteries (PCA)• "fetal" posterior cerebral artery• Inferior division of the middle cerebral artery

(parietotemporal branch)• Posterior callosal branch of Anterior cerebral

artery (ACA)

MRA

Superior sagittal sinus

IJV

Hanaway, J, et al: The Brain Atlas: 1998, p 28.

Clinical Effects of Occipital Lobe Lesions

• Visual Field Defects• Cortical Blindness• Visual Anosognosia (Anton Syndrome)• Visual Illusions (Metamorphopsias)• Visual Hallucinations

The Visual Agnosias

• Visual Object Agnosia• Visual Simultanagnosia• Balint Syndrome• Prosopagnosia• Visual Agnosia for Words (Alexia Without

Agraphia)

Visual agnosia Vs Amnesic aphasia– Description of the use of the Object– Hesitancy and uncertainity

• Color AgnosiaColor naming defect Vs Amnesic aphasia

immediate cognizanceacceptance

Eye fixation & movement abnormalities

• Psychovisual reflexes– Fixation reflex– Optically elicited fixation movement– Follow movement– Convergence/divergence– Corrective fusional movements (Holmes 1938)

Visual memory,visualization and the visual elements of dream

Charcot-Wilbrand syndromevisual agnosialoss of visualizationloss of visual elements in dreaming

Effects of unilateral disease, either right or left

A. Contralateral (congruent) homonymous hemianopia, which may be central (splitting the macula) or peripheral; also homonymous hemiachromatopsia

B. Elementary (unformed) hallucinations—usually because of irritative lesions

Effects of left occipital disease

A. Right homonymous hemianopia

B. If deep white matter or splenium of corpus callosum is involved, alexia and color-naming defect (optic aphasia for color)

C. Visual object agnosia

Effects of right occipital disease

A. Left homonymous hemianopia

B. With more extensive lesions, visual illusions (metamorphopsias) and hallucinations (R>>L)

C. Loss of topographic memory and visual orientation

Bilateral occipital disease

A. Cortical blindness (pupils reactive) B. Anton syndrome (visual anosognosia, denial of

cortical blindness) C. Loss of perception of color (achromatopsia) D. Prosopagnosia (bilateral temporooccipital

including fusiform gyrus), simultanagnosia (parietooccipital)

E. Balint syndrome (bilateral dorsal [high] parietooccipital)

Anton's syndrome

Anton-Babinski, or denial visual hallucination syndrome; cortical blindness with denial

The Balint (Balint-Holmes) syndrome

• “psychic” impairment of visual fixation and alterations in visual attention.

• optic ataxia• optic apraxia• The patient can see only one object and

cannot move his eyes from it, but he cannot reach out and take it.

• Bilateral parietooccipital lesions.

Cortical blindness Vs Hysteria

Menace reflexOptokinetic ReflexBlink ReflexEEGAssociated Neurologic deficit

Tests for Occipital lobe disorders

Color naming, color form association, and visual memory,recognition of faces of prominent people, map drawingColor matching tests (Nagel cards)Weigl’s color-form sorting testPhotograph of famous personVisual field test

Occipital lobe and Seizure

• Relatively uncommon• Lacks recruiting response• 25% of cases (Gibbs 1932, whitty 1955)• Generalized seizure > focal

Russell & Whitty 1955

Primary visual cortex (area 17)

• Elementary, unformed visual hallucinations, such as scotomas and flashes of light

• Experience of moving lights, colored• From periphery to centre• Zig-zag or weaving patterns• Showers of lights• Darkness

(Penfield & Jasper 1954, Russell & Whitty 1955)

Area 18,19

• Lights immobile, Intermittent• Twinkle, pulsate• Darkness (hemi field/total) commoner• Formed visual hallucinations.• Complex visual hallucination-

• OL(anterior part) or • Posterior temporal or • Parietal cortex

D/D Visual hallucination

• Vascular insufficiency (PCA)• Migraine episode• Basilar artery insufficiency• AVA (posterior)• VA compression in Cxl Spond.• PCA compression in Tentorial Herniation

Occipital lobe seizures

• A/w Visual symptoms (Taylor et al,2003)

• Elemental visual sensations (Bien CG, Benninger FD, Urbach H, et al: Localizing value of epileptic visual auras. Brain 123:244, 2000)

• Red>blue>green>yellow (Gowers WR: Epilepsy and Other Chronic Convulsive Diseases: Their Causes, Symptoms and Treatment. New York, Dover, 1964 )

• Momentary blindness in both fields

• A sensation of twinkling or pulsating lights. (lesions on the lateral surface of the OL, BA 18,19)

Occipito-temporal-parietal junction

• complex or formed visual hallucinations• Macro/micropsia• Metamorphopsia• Visual hallc.• Complex-colorful• Autoscopy (rare)

Ocular movement abnormalities

– Oculoclonic – Oculogyric deviation– Clonic palpebral jerks– Forced closer of eyelids– Forced eye turning (parieto-occipitlal)

Childhood epilepsy with occipital paroxysms

• Heterogenous• Late onset- Gastaut type• Panayiotopoulos syndrome

Taylor et al, Brain,vol 126, pp 753-769;2006

Gastaut- type occipital epilepsy

Onset : 3-16 yrs of age# Visual hallc.Ictal blindness,amaurosis,Tonic deviation of eyesLast <1 min.Hemiclonic/cps/GTCSBehavioral/Autonomic features- rareRemits within 2-5 yrs in 50-60%

EEGInterictal - high amp,2-3 hz SSWc(posterior quadrant)Ictal-prominent occipital discharge with spread +

Panayiotopoulos syndrome

Age 3-6 yrs (1-14 yr), Seizures-InfrequentSeizures during SLEEP Autonomic (vomiting,palor,sweating etc)Behavioral features (irritability)Autonomic epilepsy (Ferrie et al, 2006)Last for HOURS in 1/3rd

Good prognosis (remit 1-2 yrs) AED – unnecessaryEEG

Ictal:# posterior slowinginterictal: same as Gautaut-type

Idiopathic photosensitive occipital epilepsy

• Between 5-17 yrs• Watching TV, video game• Colorful moving spots in the PFoV• Tonic head & eye version• Nausea/vomiting/sharp pain in the orbit,head• Unresponsiveness• Cognitive state/neurological exam- normal• IIEEG: b/l sync or asynch occipital spikes & SWCs• IEEG: Occp. Epileptiform activity (shifting)

Conditions a/w occipital discharges

• Lafora‘s disease• Mitochondrial disorders• Malformation of Occipital cortical

development• OE with b/l Occipital calcifications• Celiac disease