Gebruiker:Carlotta Wolf/Kladblok

Introduction

Patient N.A. (July 9, 1938 - ) - American, who developed anterograde amnesia as a result of an accident. He was a patient studied by Larry Squire - a professor of psychiatry, neuroscience and psychology at the University of California. The cause of his amnesia was found to be a thalamic lesion extending to the hypothalamus. Damage to the temporal cortex was also found and thought to be a result of an exploratory surgery.

Patient N.A.’s accident happened when he was 22 years old (1960). A fencing foil went up his nose and injured his brain. This resulted in severe anterograde amnesia, especially for verbal material, as well as impaired eye movements. His cognitive abilities remained intact.

Since the accident, N.A. attended examinations in MIT laboratories and received home visits. Later, his case was studied and described by Larry Squire. CT scans and MRI findings revealed a large diencephalic lesion, involving left thalamus, hypothalamus, floor of the third ventricle and mammillary bodies. Damage of the right temporal lobe was also found, possibly due to an operation N.A. underwent (undetermined). [2]

The accident

In 1960 N.A.’s brain was accidentally damaged by a miniature fencing foil.

N.A. was 22 years old at the time he acquired his injuries. When he was 48 with the help of magnetic resonance imaging (MR) researchers found three areas that were damaged. N.A.´s injuries were studied by the neurologist Larry Squire and played an important role in the development of theories that explain the link between brain function and memory.[1]

Neuropathology

Patient NA underwent multiple neuroimaging studies using Computed Tomography (CT) and Magnetic Resonance Imaging.[2]

His first CT was conducted in 1977, followed by another examination in 1983.

NAs brain abnormalities included a hypodense region in the left thalamus in both examinations. In the 1983 examinations, an enlarged right temporal horn of the lateral ventricle was found.[2]

Four magnetic resonance imaging studies were conducted on NA, from 1986 to 1987. Diencephalic abnormalities were found including damage to the left thalamus extending anteroposteriorly into brain nuclei. Patient NAs brain damage likely disrupts the mammillothalamic tract and postcommissural fornix. The posterior hypothalamus is disrupted and the mammillary are missing in both brain hemispheres. His right anterior temporal lobe is damaged. [2]

Neurologists interpretations of NA's symptoms

Due to his injuries three major areas of the brain were damaged, leading to his severe amnesia.  Based on other studies doctors inferred that amnesia is a result of the conjointly damaged diencephalic structures, such as the internal medullary lamina, the intralaminar nuclei, the mediodorsal nucleus, and the mammillothalamic tract.

At first, after undergoing a series of CT scans, it was assumed that the region of the mediodorsal nucleus was affected by a left thalamic lesion. After further investigations using magnetic resonance imaging it was shown that his lesion was more extended. According to the tests he underwent, he suffered from a memory impairment related mostly to verbal material rather than the nonverbal one; however it was difficult to understand what damaged area was responsible for this effect.

The damage in the mammillary nuclei itself was not related to the type of memory impairment that the patient N.A suffered from but rather influencing it through the combination with the damage that occurred in the thalamic structures.

1

Squire, L. R., Amaral, D. G., Zola-Morgan, S., Kritchevsky, M., & Press, G. (1989). Description of brain injury in the amnesic patient N.A. based on magnetic resonance imaging. Experimental neurology, 105(1), 23–35. https://doi.org/10.1016/0014-4886(89)90168-4

2

Squire, L. R., Amaral, D. G., Zola-Morgan, S., Kritchevsky, M., & Press, G. (1989). Description of brain injury in the amnesic patient n.a. based on magnetic resonance imaging. Experimental Neurology, 105(1), 23–35

3

Squire, L. R., Amaral, D. G., Zola-Morgan, S., Kritchevsky, M., & Press, G. (1989). Description of brain injury in the amnesic patient n.a. based on magnetic resonance imaging. Experimental Neurology, 105(1), 23–35.