931-4 Convergence Insufficiency

History A 73-year old man with known PD for 10 years, complained of horizontal double vision for 18 months. He could see the images move apart and refocus a single image by blinking. Diplopia was most marked reading, driving and watching TV. Three ophthalmologists gave him 3 separate sets of glasses. Past hx –ve for strabismus or prism glasses.

Presenting Symptoms Difficulty walking Generalized rigidity Tremor of the hands at rest Diplopia reading

Ocular Motor Signs Impaired convergence Slow hypometric saccades Saccadic substitution for smooth pursuit Poor visual suppression of the vestibular ocular reflex Decreased spontaneous blink rate Glabella tap positive

Neurological Signs Rigidity of the neck, head flexed and tilted Mild head tremor Mask-like face Slow (akinetic) head and neck movements

Convergence Insufficiency Three factors: Age Parkinson’s disease Medications (Sinemet)

Etiology of Slow Saccades Spinocerebellar Ataxias (SCA), especially SCA2 (olivopontocerebellar atrophy) Huntington’s Disease Progressive Supranuclear Palsy Parkinson’s (advanced cases) and related diseases. Lytico-Bodig disease

Slow Saccades Whipple’s Disease Wilson’s Disease Amyotrophic Lateral Sclerosis (some cases) Drug intoxications: anticonvulsants, benzodiazepines

Courtesy of Mendez F. Cummings JL. Dementia: A Clinical Approach. Third Edition. Butterworth Heinmann 2003.

The following illustrations of The brain MRI Pathology of the midbrain Lewy body are taken from the case of an elderly woman with Parkinson’s Disease.

Figure 1 Axial T2WI through the midbrain shows the normal pars compacta, the space between the substantia nigra and red nuclei.

Figure 2 Axial T2WI in a patient with PD shows the midbrain is atrophic and the red and substantia nigra almost touch each other because the pars compacta is greatly reduced. Courtesy Anne Osborn, MD

Figure 3 Axial gross autopsy in patient with PD shows striking reduction of the pars compacta, especially well seen on the right side where the red nucleus and substantia nigra are actually touching

Figure 4 Section of the brain showing cytoplasmic inclusion body within a surviving neuron with an eosinophilic core surrounded by a clear halo. The Lewy body is not entirely specific, but it is a highly sensitive marker for PD

Parkinson’s Disease Due to dopaminergic cell death leading to dopamine deficiency Defective gene for  synuclein on Chr. 4q Second locus on Chr. 2p