A Little Known Fact: Very Late Onset Autism

Autism is presently recognized as a neurodevelopmental disorder. This means that sometime during gestation brain development is disturbed. Fingerprints indicative of migrational abnormalities and cortical malformations support the premise that autism is a neurodevelopmental disorder. This perspective argues that variability within the genetic makeup of the individual, exogenous/environmental factors, and timing during brain development all account for the heterogeneity of clinical symptoms observed in patients (the so-called Triple Hit Hypothesis, see http://bit.ly/19yLAzL ). Given the neurodevelopmental nature of the disorder it is unsurprising that onset of symptoms is usually observed early during postnatal development. In effect, the older criteria included in the Diagnostic and Statistical Manual (DSM IV-TR) stated that in order to obtain the diagnosis of Autistic Disorder the individual would have to manifest considerable and characteristic impairments in social interaction, communication and range of interests and behavior before 3 years of age. This age of onset criteria has now been removed from the DSM5.

With the introduction of the DSM5 childhood disintegrative disorder or late onset autism was supposed to be subsumed into the larger autism spectrum disorder category. According to writings from the working committee for the DSM5, “We believe that children meeting the DSM-IV-TR criterion for childhood disintegrative disorder will now fit well within the new diagnostic criteria for autism spectrum disorders” (see http://bit.ly/1M5K3TB ). However, other statements within the DSM5 make this a dubious conception. Although the age of onset criteria has been removed, the DSM5 still claims that, “Symptoms must be present in the early developmental period (but may not become fully manifest until social demands exceed limited capacities, or may be masked by learned strategies in later life)”. Adults may thus be diagnosed with Autism Spectrum Disorders but their symptoms are presumed to have developed gradually. In these cases the DSM5 suggests that symptoms may have been subtle but always present.

Unfortunately modern criteria do nothing to clarify the ongoing debate as to the status of regressive, disintegrative, acquired or late onset autism (all the aforementioned terms are synonyms). These are individuals who develop normally but then start to lose speech and social skills between the ages of 15 and 30 months of age. Studies, including some that have been video substantiated, point to a number of cases that qualify as regressive autism. Is this a valid diagnosis? Is it the same as the disorder described by Kanner? Some autistics who may have “developed a vocabulary” could have been parroting sounds (also called echolalia). This has given rise to still another debate as to whether social and language regression should be treated equally when considering a diagnosis of late onset or regressive autism.

In this blog we are not going to discuss the nature of regressive autism but rather expand on a subject that has been readily accepted by most clinicians: the case of adolescents or adults who were unquestionably normal and then developed symptoms diagnostic of autism. These are cases where an inciting cause was known and would thus be labelled as non-idiopathic autism. The underlying causes in these cases are multiple and include mitochondrial disorders, anti NMDA receptor encephalitis, herpes infection, etc. These disorders have in common that they affect large areas of the brain and, by damaging the cerebral cortex, promote seizures.

In this blog we will talk primarily about herpes simplex encephalitis as a cause of late onset autism. Encephalitis denotes inflammation of the brain. Symptoms associated with brain inflammation include fever, a change in the state of consciousness (drowsiness, stupor or coma), alterations in personality, flu-like symptoms, unsteady gait, headaches, confusion and seizures. Common causes of encephalitis include viruses, bacteria, chemicals, and autoimmune reactions.

The most common virus to come to a Neurologist attention because of encephalitis is herpes simplex. This is the same virus that causes common cold sores. Fifty seven percent of American adults are infected with this virus as it lies dormant within one of our cranial nerves. The encephalitis is caused by the retrograde transmission of a reactivated herpes simplex virus along a nerve axon (most probably the olfactory pathway or trigeminal ganglia) and into the covering of the brain. From the coverings of the brain the virus infects the adjacent temporal and inferior frontal lobes first, and then spreads to the rest of the brain. Neuropathological examination reveals a greater degree of brain destruction, inflammation and reactive response than in any other viral encephalitis. The localization within the frontal and temporal lobes helps explain why the patients often display bizarre behaviors, personality changes, anosmia and gustatory hallucinations.



DeLong and colleagues (1981) described 3 children (age range of 5 to 11) who developed an acute encephalitic disorder accompanied by autistic features that resolved after clinical recovery. In 2 of the patients the inciting agent was never identified. However, the third patient had high serum titers for herpes simplex and a computerized tomography (CT) that revealed extensive lesions of the temporal lobe, primarily the left side. Ghaziuddin and colleagues (1992) reported two cases that developed herpes infection in either the intrauterine or early postnatal period and presented features of autism at approximately 2 years of age. In contrast to the previous cases where imaging suggested a predominant involvement of the temporal lobes, Ghaziuddin and colleagues (2002) reported the case of an 11-year-old child who developed symptoms of autism following herpes encephalitis involving the frontal lobes. Another case report came from Gillberg (1986) who described a 14-year old girl who developed a “typical” autistic syndrome as a result of herpes simplex encephalitis. The autistic symptoms persisted long after the acute symptoms of the encephalitis abated. Greer and colleagues (1989) reported a 14-year old boy who was normal till the second grade when he was hospitalized with herpes encephalitis. He later developed significant and persistent social, language and memory deficits. This and other cases where autism developed after an infection at an older age indicate that, at least in syndromic cases, autism is not necessarily a neurodevelopmental disorder (Gillberg 1991).


Delong GR, bean SC, Brown FR III. Acquired reversible autistic syndrome in acute encephalopathic illness in children. Archives of Neurology 38:191-194, 1981.

Ghaziuddin M, Tsai LY, Eilers L, Ghaziuddin N. Brief report: autism and herpes simplex encephalitis. J Aut Dev Dis 22(1):107-113, 1992.

Ghaziuddin M, Al-Khouri I, Ghaziuddin N. Autistic sympttoms following herpes encephalitis. Eur Child Adolesc Psy 11(3):142-6, 2002.

Gillberg C. Brief report: onset at age 14 of a typical autistic syndrome. A case report of a girl with herpes simplex encephalitis. J Aut Dev Dis 16:369-375, 1986.

Gillberg C. Autistic syndrome with onset at age 31 years: herpes encephalitis as a possible model for childhood autism. Dev Med Child Neurol 33(10):92-4, 1991.

Greer MK, Lyons-Crews M, Mauldin LB, Brown FR III (a989) A case study of the cognitive and behavioral deficits of temporal lobe damage in herpes simplex encephalitis. J Aut Dis Dev Dis 11:317-330, 1981.

14 responses to “A Little Known Fact: Very Late Onset Autism

  1. Dr. Casanova,

    I am writing as a parent of a 22 y.o with profound autism. He is low functioning ( IQ imperfectly measured at 40) and has some words, but essentially non verbal. Legally, he is adjudicated incompetent. He met the standard of yours ( others) of showing symptoms of “regressive” behavior, being symptomatic of high fever, etc. immediately following vaccinations at age 18 months. No amount of intervention with widely accepted therapies have made any perceptible changes.
    As you know, establishing blame is futile when one is looking for solutions. Even though I have taken some measures which may be thought of as “unorthodox”, they have been harmless to our son.
    How does one ( or we as a societal whole) go about a scientific pursuit for an individuals root cause similar to my child’s case. Over 20 years and numerous encounters, I know that the facts are not terribly dissimilar to many other people. Thank You.


    • “How does one ( or we as a societal whole) go about a scientific pursuit for an individuals root cause similar to my child’s case.” My approach has been as follows: there are cases of autism for which we do not know the cause (idioppathic) and some for we do know the cause (syndromic). I have taken many syndromic cases for which the brain pathology was well established and sought what they had in common. The result is that they exhibit migratory abnormalities of neurons during brain development. This helps explain phenomena like seizures, mental retardation and sensory abnormalities.
      Thanks for the comment.


      • Not all of those with syndromic conditions develop autism. Fragile x patients have it 50% of the time but not 100%. I wonder why? Also what does the encephalitis do to cause specifically autism? What IS autism? Not what can cause it, or what are the effects. But what makes autism autism in the brain? What is the one unifying feature in autistic patient’s brains? A person with fragile x is able to not have autism, so if you compare the brain of someone with autism and fragile x and one without autism and only fragile x, what is the difference? The neural migration may trigger autism, but why not always?

        Liked by 1 person

      • All good and appropriate questions. As you said there is much to be investigated. I wish I had the answers. However, we are moving forwards even if it is in baby steps. Thanks


      • “What IS autism? Not what can cause it, or what are the effects. But what makes autism autism in the brain?”

        These questions were answered long ago as can be seen in Chapter 7 of Experts Catastrophe at http://www.pseudoexpertise.com .

        Note that I (Robin Clarke) have never been of a view that autism was a developmental disorder anyway. Also, (as elaborated a bit in Chapter 3), I consider that autisticness is not a characteristic of the brain or even the body, but only of the relationship of the living being to its particular environment. A person who is well-adjusted in a research library could be very “autistic”-maladapted in the company of football hooligans.

        As for the notion that other researchers are advancing only in “baby steps”, discretion restrains me from commenting here….


  2. Dr Casanova,

    I have just read this article with great interest having only heard vaguely that The Herpes Simplex Virus is a suspected cause of Autism.

    My son who is now 3+ was diagnosed with ASD close to a year ago. He like many others seemed to be developing typically though there were some complications during pregnancy (Choliostasis and he was born with his head considerably pressed to one side – now all ok as he has developed)

    What has interested me is the thought that the Herpes virus could have caused his ASD. He did have cold sores on at least 2 or 3 occasions from after 1yr old and like his sister had reoccurring tonsillitis with a number of hospital visits and antibiotics.

    My question is, is there anything that can be done at this point to strengthen his immune system against the Herpes Virus, or anything that can be done do help ensure the virus does not reoccur? anything to help to get rid of the virus from his system?

    Thanks in advance



    • The cases of herpes that could account for an autism-like phenotype (presentation) were primarily those that caused brain infection (encephalitis). In those cases the temporal lobes are affected with some of its tissue dying and having multiple hemorrhages. I would not be bothered much with your son’s cold sores. Many people have them without any type of progression into autism. Hopefully this reassures you. Let me know if I can be of any additional help.


  3. Dr. Casanova,

    This article is very interesting. I’m 34 years old and never been officially diagnosed by a trained professional. Recently, a lot of people think I’m autistic and I’m starting to wonder why so I did a little research online and read many articles and even took some online test to determine if I am on the spectrum. Just a little back ground. I was never diagnosed as a child because I never showed any signs. I was like any other kid who loved to play, make friends and a bit of mischief. I have experienced chronic stress since childhood and had some relief when I reached 18 years old til early 20’s but didn’t last long and I experienced yet again more stress being with my toxic partner for 3 years. I also acquired a sexual virus from my partner and now a carrier. I tried to commit suicide and fell head first on tiled floors. After I was discharged from the hospital and while trying to recover, I became a bit indecisive, paranoid, disorganized, my personality just changed basically from confident, easy going, composed, appropriate in conversations to anxious, highly emotional (more than before), more lose sexually, gullible, suggestible, couldn’t concentrate, messier at home, lack of energy or too much of it, sometimes I tend to repeat things like locking the door 2x, and repeat questions or things in conversations 2-3 times and became more forgetful, I have no filter and talk about even inappropriate things in details, I easily get confused, I space out and can’t understand what someone is saying, I stammer a bit when nervous and mispronounce words I normally wouldn’t mispronounce. It was really hard for me and my family but now I’m trying to concentrate more on improving myself and it seems to be working but essentially still the same. What is wrong with me and will I ever be my normal self again? Could I have mental illness initially and later after the fall caused damage to my brain or maybe the virus I got from my partner? I am lost Dr. Please help.


    • You need a full work up by a neurologist. You could have had a contusion from the fall. In addition, chonic viral infections (like herpes) which otherwise are associated with cold sores have been recently found to promote cognitive problems like memory loss.


    • Gosh, what a case report. I am just wondering, as a supplement to what Dr Casanova suggests here, the possibility of a mercury connection, though I emphasise not a certainty, and especially with those other potential factors present.

      A number of words in your comment are suggestive of possible mercury toxicity from dental amalgams (generally acquired in early teens):
      “I have experienced chronic stress”
      “I experienced yet again more stress”
      “I tried to commit suicide”

      And all these others below here read very suspiciously like mercury poisoning — a subject I know far more about than I ever wanted to:
      “I became a bit indecisive, paranoid, disorganized, my personality just changed basically from confident, easy going, composed, appropriate in conversations to anxious, highly emotional”
      ” couldn’t concentrate, messier at home, lack of energy or too much of it”
      “I tend to repeat things like locking the door 2x, and repeat questions or things in conversations 2-3 times and became more forgetful”
      “I easily get confused, I space out and can’t understand what someone is saying,”

      A possibility is that when you had the (presumably) brain trauma from the fall, that could have let some of the mercury get into the brain (which is normally largely sealed from mercury by the blood-brain-barrier). Alternatively (or additionally) such a major stress can knock out the mercury detox processes such as glutathione.

      CHRONIC mercury poisoning is just about impossible to diagnose (***notwithstanding that plenty of “experts” will insist otherwise!***). The best causal indicators are (1) have you been exposed?, e.g. a number of amalgams for some years; or incompetent drilling of amalgams without proper ventilation; and (2) competently removing the source and competently detoxing (merc detox can be VERY harmful if your expert isn’t as expert as you hoped, in my experience there are approximately no real experts), and seeing if things have improved after one or a few years (took six years in my case but that is v exceptional). Commonly, a brief but striking recovery occurs soon after amalgams removal but then the merc starts “liberating” and symptoms resume.

      A good start could be to take 200-400 mCg of selenomethionine (mercury “antidote”) a day and see if it improves. I myself had to take much more but for some others even 400 mCg could be too much (the C there is rather important!).
      Be very bewared of lipoic acid, chlorella, and coriander (main thing in curry), all of which can turn you into a vegetable even if your “expert” insists otherwise.
      By the way, your writing there was very clear and competent, as with Dr Casanova’s in fact!


    • “Could I have mental illness initially”

      The data I have found myself suggests that just about all “mental illness” (though certainly not ALL of it) has a significant involvement of mercury poisoning in it. As most clearly indicated in graphs 3.5 and 3.7 in Chapter 3 of “Experts Catastrophe” at www,pseudoexpertise.com. Torrey’s research suggests that mental illness was virtually non-existent before mercury became used (as European society became more “developed”). His research was prevented from publication, as my own in due course has been too.


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  5. (At risk of overstepping a quota on this page….) Re Dr Casanova’s quotation of the Gillberg 1986 case, my 1993 paper also cited it (as per my book at page 215), and says the 14 yo’s autism lasted 70 days. Which is curious given that most autism lasts enduringly. This is compatible with my view that the unifying principle of autism causation is not some particular chem-molec-physical pathway but rather the relatively abstract concept of interference in all/any of the processes expressing from genome to functioning being. Some autisticness would be caused at the migratory level as identifed by Manuel, but some other could be at a level of transient chemical messengers. And yet other similar behaviour due to lack of socialising environment (the Wild boy of Aveyron?).


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