Diagnostic Error

(March 20th, 2015) Everyone studying neuroscience knows Henry Molaison or at least his initials, H.M. His epilepsy and post-surgery amnesia was the base for numerous scientific publications. A recent study, however, finds that HM’s disease was most probably misdiagnosed.

Henry Molaison was born in Hartfort, Connecticut, in 1926. As 7-year-old boy he had a bicycle accident and as a consequence developed epilepsy. It got worse towards the end of his twenties. A typical symptom of epilepsy is seizures or vigorous body shakes. After unsuccessful treatment by many doctors, he was eventually referred to surgeon William Beecher Scoville at Hartford Hospital. Even though Scoville was an authority in brain diseases, he could not explain the main cause of HM’s seizures. As a result, Scoville proposed an experimental operation to remove major parts of HM’s temporal lobes, including the hippocampi, in 1953. After the surgery, the seizures were gone but also some of HM’s memories.

HM’s amnesia showed scientists throughout the world that memory can be classified into different types such as procedural and declarative memories. HM’s procedural memory was unaffected: he could learn skills and perform better with more practice. However, he did not remember how he learned those new skills: his declarative memory was impaired. After the operation until his death HM remained in care in Windsor Locks, Connecticut. He was under daily scientific investigations until December 2nd, 2008, when he took his last breath. During that night, in vivo, in situ, and ex vivo high-resolution MRI data of his brain were collected and made available for researchers worldwide. Undisputedly, his case is a cornerstone of cognitive neuroscience.

But the purpose behind HM’s operation is highly questionable. How could a massive surgical operation be performed on a human being without solid reasons? Francois Mauguière at the Neurological Hospital in Lyon, France, and Suzanne Corkin from Massachusetts Institute of Technology argue in a recent paper that the bilateral surgical destruction of some parts of HM’s temporal lobes was a complete mistake. Why? Because “he did not have temporal lobe epilepsy”. Studying HM’s medical history, Mauguiére and Corkin concluded that the patient suffered from idiopathic generalized epilepsy (IGE). People suffering from IGE have no brain abnormalities, meaning that this disease has no specific locus within the brain. As a result, removing parts of the brain will not treat the patient’s epilepsy.

Before the operation, Scoville admitted that he had no definite explanation for the cause of HM’s seizures. In addition, Scoville was a neurosurgeon, influenced by the psychosurgery movement. He believed that by making cuts in the brain, the seizure threshold would be increased, making the brain function normally again. This, according to Scoville’s hypothesis, would cure HM’s epilepsy.

Mauguière and Corkin argue that at the time of the operation doctors did not know that temporal lobes of the human brain were responsible for memory processing. That is why Scoville “was so surprised by the striking and totally unexpected memory loss” after the operation.

A somewhat lucky coincidence then, for science. Henry Molaison’s surgery-inflicted amnesia spawned scientific discoveries that contributed to our understanding of the workings of the human brain. But was it really worth its price?

Nadejda Capatina

Photo: S. Corkin

Last Changes: 04.28.2015

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